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Subject: Geographic Information Systems FAQ

This article was archived around: 15 Apr 1997 16:44:19 -0400

All FAQs in Directory: geography
All FAQs posted in: comp.infosystems.gis
Source: Usenet Version


Archive-name: geography/infosystems-faq Posting-Frequency: monthly Last-modified: 1997/03/13
URLs: ftp://ftp.census.gov/pub/geo/gis-faq.txt ftp://abraxas.adelphi.edu/pub/gis/FAQ http://www.census.gov/geo/www/faq-index.html (pretty hypertext version of this document) Frequently Asked Questions and General Info List (Long! > 3200 lines) Periodic Posting to GIS-L and comp.infosystems.gis GIS FAQ List (97-03-13) This is the list of frequently asked questions (FAQ) about Geographic Information Systems (GIS) along with answers to these questions.* This FAQ is posted as a resource to the `comp.infosystems.gis' newsgroup which is connected to the GISL LISTSERVER mailing list. 1. Administration: 1. How do I get the FAQ list? 2. What is the difference between the newsgroup and listserv? 3. Can I post a commercial advertisement to this list/group? 2. Research and Universities: 1. What in the world is a 'GIS'? 2. What colleges and universities offer coursework in GIS? 3. What are the NCGIA anon ftp sites and what can be found there? 4. Where is that On-Line GIS Bibliography (and what's in it)? 3. Data Formats and Map Products: 1. What are the United States map accuracy standards? 2. What is the Vector Product Format and where can I get information? 3. What is this SDTS thing and is it available via ftp? 4. What is a DXF file and where can I get info about it? 5. What is DEM and where can I find out about some? 6. Where can I get information about TIGER/Line? I heard there is a terrific new and improved 1992 release... 7. How do I order USGS maps? 8. What is the Digital Chart of the World (DCW) and how do I get one? 9. Is there a package available to convert from UTM to latitude/longitude? 10. Does a file exists of latitude and longitude of US cities? 11. Where can I get old antique maps? 12. Is there a standard for representing latitude and longitude? 13. Has anyone compiled a list of standards and formats? 4. Other Sources of Information: 1. What are some other related mailing lists, ftp sites and internet sources for useful resources? 2. Hey! But how do I subscribe to GIS-L, MAP-L, etc? 3. What are some books and magazines available on GIS? 4. Where can I get a copy of the SpatioTemporal Bibliography? 5. What professional organizations are out there for GISers? 6. What are some journal titles which carry GIS articles? 7. How can I subscribe to the Int'l Journal of GIS? 8. What are some World Wide Web URLs for GIS information? 9. Where can I find pointers to satellite data? 10. Are any mailing lists archived anywhere? 11. Can you recommend any other resource documents? 12. Can you point me towards some on-line job resources? 5. Technobits: 1. What are some algorithms for calculating the distance between 2 points? 2. What is GPS? 3. What can you tell me about map projections? 6. Software Issues 1. What are e-mail and paper addresses of some vendors? 2. What public domain or shareware GIS software is available and where is it? 3. Will GRASS run under LINUX OS on my PC? 4. How can I convert ARC files to IDRISI? 5. How can I convert ARC coverages to GRASS? 6. Where can I find some AMLs to look at? 7. How can I convert ARC files to some other graphics formats? 8. How do Arc/Info and Intergraph MGE compare? Netiquette ---------- If someone asks a FAQ, please e-mail the answer instead of posting. You should also include information on how to access the FAQ. (see question 1) If you have information that you think should be included in the FAQ, please e-mail the information to Lisa Nyman <lnyman@census.gov>. Feel free to discuss the information on the net to get a consensus if the answer is canonical. If you believe that some information in the FAQ is wrong, please e-mail us. We don't want the FAQ to generate more postings than it saves! We are not the authors of much of this information, only the compilers. We will work with you and the author to resolve the issue. Credit is given for contributing information gotten from the Net. Avoid flamewars. When you get the urge to flame, wait until the urge goes away. ________________________________ Q1.1: How do I get the FAQ list? The most current version is available via anonymous FTP on ftp://ftp.census.gov/pub/geo/gis-faq.txt ftp://abraxas.adelphi.edu/gis/FAQ Use your favorite WWW browser and take a peek at: http://www.census.gov/geo/www/faq-index.html To get the FAQ in plain text (mail message > 100K), send a mail message to gis-faq-request@abraxas.adelphi.edu Content doesn't matter (null message is ok). If you wish to receive a gzip'ed and uuencoded version of the FAQ (about 50% compression), specify 'gzip' or 'gzipped' (case doesn't matter, only the first 4 characters are significant) on the 'Subject:' line of the message. Caveat: your mailer must supply a valid 'From:' return address. To contribute to the FAQ, send mail to lnyman@census.gov ______________________________________________________________________ Q1.2: What is the difference between the newsgroup and listserv? The newsgroup comp.infosystems.gis is a Usenet special interest news distribution scheme that allows individuals with access to Usenet to read and post articles. The system is somewhat like e-mail but involves a network of news 'feeds' that pass the news along. The listserv system is a mailing list of e-mail addresses which allows members to send messages to the GIS-L mailing list. The GIS-L mailing list consists of a large number of people interested in GIS who receive GIS related articles using their normal e-mail software. Check with the systems administrator(s) at your site to see if you receive USENET news or if a site mail alias has already been set up for the mailing list before subscribing. This will help cutdown on network traffic. Articles sent to either of the above will be sent to the other so there is no need to post to both groups. [PLEASE NOTE: IF YOU READ GIS-L AND REPLY TO A MESSAGE, YOUR REPLY MAY SENT TO THE ENTIRE LIST, NOT JUST THE ORIGINAL SENDER OF THE LETTER. KNOW THY MAILER!] A note to Usenet posters: To avoid the above problem, if you are posting something like "Send me mail if you want a copy of..." set the Followup-to: line in the post header to 'poster'. Please use meaningful subject headings. For example, 'TIGER: How do I determine boundaries?' is preferable to 'Duh! Need help'. ** Place job title and location in the subject line of job announcements. It is important that people remember that messages to GIS-L end up on Usenet and those with Usenet access should read new user information in the news.announce.newusers group. One highlight to note is that while product information can be valuable to a group, please post only one article per product, as this should -not- become a commercial advertisement center (See 1.3 below). This is not a moderated group or list so sometimes irrelevant junk gets posted. Please ignore such posts and let them dissappear. Also, please keep .signatures to a reasonable number of lines. ______________________________________________________________________ Q1.3: Can I post a commercial advertisement to this list/group? In principle, announcement of professional services or products on Usenet newsgroups is allowed. Because GIS is still a relatively immature field, resisting commercial postings on GIS-L may mean that genuinely useful information, which is of interest to a majority of subscribers, is lost. However,because commercialisation of the internet is racing forward, we must have strict guidelines if GIS-L is to remain a useful discussion forum. Therefore, for GIS-L, the following guidelines for COMMERCIAL postings will apply: (1) The product which is the subject of the announcement must be directly related to GIS. This not the place to announce your new graphics package. (2) Messages should be short (20 lines or one screen page) and should reference any extended information through a user-request facility (such as an email address, ftp, WWW etc.). (3) The address used to post the message must be a valid, accessible internet email address which individuals can REPLY to. The "Reply-to" address header in the message must point to your personal email address - not to GIS-L. Where you are posting to the newsgroup, make sure the "Follow-up" header field is set to "poster" and NOT to "comp.infosystems.gis". (4) Messages advertising a product must have an informational content greatly in excess of their promotional content. Superlative adjectives should not be used. Stick to technical facts. (5) Messages of a purely advertising nature, as distinct from product announcements should not be posted. (6) An organisation should restrict themselves to occasional announcements (no more than one per month). Messages should not be repeated unless they contain new or updated information. (7) The product must be of truly INTERNATIONAL interest. Announcements relating to niche products or only of limited regional applicability are not encouraged unless reflecting significant new or unique development which is likely to be of genuine interest to GIS-L readers. (8) It is good practice to assist readers by using informative subject fields, for example "Advert:", "Product Announcement:" or simply "AD:" prefixing a three or four word description of your message. Blank subject fields should be avoided at all costs (personally I ignore all such messages). Using a prefix and informative subject make it much more likely the people you want to read your message will actually read it. If you are not sure whether your proposed posting meets these guidelines then DO NOT POST to GIS-L. There is an excellent alternative, if you are using news, then full press releases, product announcements and any promotional materials can be posted to the group "comp.newprod". Where an individual regards that these guidelines have been broken they should email the POSTER and tell them so. Please draw their attention to this entry in the FAQ. A large amount of incoming email is a very effective means of discouraging the poster from breaking the rules in the future. Please make sure you email the POSTER and not THE LIST (check the reply address before you use the reply function of your mailer. Failing to check this will result in you receiving lots of email for GIS-L readers unhappy about your behaviour! This policy may be subject to change in the light of new circumstances. Thanks to Bruce gittings <BRUCE@geovax.ed.ac.uk> ______________________________________________________________________ Q2.1: What in the world is a 'GIS'? From: Scott Freundschuh What Is A Geographic Information System (GIS)? An information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working [analysis] with the data. (Star and Estes, 1990) A system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data which are spatially referenced to the Earth. (Chorley, 1987) Automated systems for the capture, storage, retrieval, analysis, and display of spatial data. (Clarke, 1990) A system of hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modeling and display of spatially-referenced data for solving complex planning and management problems. (NCGIA lecture by David Cowen, 1989) An integrated package for the input, storage, analysis, and output of spatial information... analysis being the most significant. (Gaile and Willmott, 1989) GIS are simultaneously the telescope, the microscope, the computer, and the xerox machine of regional analysis and synthesis of spatial data. (Abler, 1988) From: David Mark <dmark@sun.acsu.buffalo.edu> Can we come up with a definition of GIS that would provide a "truth in advertizing" product defnition for what software can be advertized as being a GIS, and what cannot,a definition which, when applied to all the packages that we agree are GISs returns "TRUE", and for the others returns "FALSE". From: dmarble@magnus.acs.ohio-state.edu (Duane F Marble) One of the distinctions is the ability to do overlay. Not draw two things on top of each other, but the logical operation. The creation of buffers via computation is also closely related. The distinction is between mapping and analysis. From time to time, theoretical discussions on this question pop-up. ______________________________________________________________________ Q2.2: What colleges and universities offer coursework in GIS? Many schools throughout the world offer coursework in GIS and related studies in different academic departments including Geography, Computer Science, and Urban Planning among others. Sources of Information: 1. Geo Info Systems May 1992, Academic GIS Directory: GIS in Higher Education. This is a list compiled by John Morgan with Barbara Fleury (Towson State University) which includes courses offered by University departments all over the world. Listing are by University, department type, and by state and country. Information in the listings include course titles, school addresses and persons to contact. 2. Guides to Geography Departments, annual publication of the AAG. [What does AAG mean? Association of American Geographers] This publications provides graduate and undergraduate programs for geography departments at US and Canadian Universities. Info provided includes faculty, program options and requirements, and lab facilities. Contact the AAG, 1710 16th Str NW, Washington DC 20009-3198 for ordering information. AAG phone: 202-234-1450 Email: guide@aag.org Note: Many faculty participate in Usenet and listserv discussions and are directly accessible via Email. ______________________________________________________________________ Q2.3: What are the NCGIA anon ftp sites and what can be found there? From: Karen Kemp <kemp@ncgia.UCSB.EDU> The National Center for Geographic Information and Analysis (NCGIA) has a publicly available ftp site as well as a WWW homepage which points at the ftp site. ftp address: ftp.ncgia.ucsb.edu WWW address: http://www.ncgia.ucsb.edu If the Santa Barbara site is unavailable, this site is mirrored at the other two NCGIA centers: University of Maine: grouse.umesve.maine.edu in the pub/NCGIA/UCSB directory SUNY Buffalo: ncgia.geog.buffalo.edu As of January 1995, about 30% of the pre-1995 technical report series are available through ftp. New reports will be added as the digital files become available. To see the full list of NCGIA technical reports, view the file "pub_list" available both at the root directory of our ftp site and inside the pub directory. To access the files in this site, ftp to "ftp.ncgia.ucsb.edu" as the user "anonymous" with any password, and "cd" into the "pub/Publications" directory. Here there are several directories: annual_reports - NCGIA annual reports biblio - GIS bibliographies final_reports - final reports on closed research initiatives pubs_list - ASCII version of the current publication list tech_reports - reports from the NCGIA Technical Report series These directories have subdirectories by year and within those are subdirectories by document. Within each of the document subdirectories you will usually find "text" and "postscript" versions. In some cases there are also other digital formats, data files and readme files. ______________________________________________________________________ Q2.4: Where is that On_Line GIS bibliography (and what's in it)? From: Duane F. Marble <dmarble@magnus.acs.ohio-state.edu> GIS MASTER BIBLIOGRAPHY PROJECT Department of Geography The Ohio State University Columbus, Ohio 43210 The first update components of the GIS Master Bibliography are now available on-line. All entries contain a full abstract (used with permission of the copyright holder) and are available in two forms: REFER - a standard ASCII file utilizing standard codes (e.g., %A) which permit use of the file with software available on most UNIX systems or it may be searched in most word processors. ENDNOTE - a binary library file configured for the commercial EndNote and EndNote Plus software (available for either the PC or the Mac). EndNote permits citation formatting for a variety of journals, automatic addition of refer- ences to papers, etc. Please feel free to copy and make use of this bibliographic material in your own research and development activities. Please do NOT redistribute all or even part of the bibliography without written permission from the publisher since reproduction of the abstracted material is governed by standard international copyright law. We wish to acknowledge the generous support of ESRI which has contributed significantly to the start-up of this activity. ********* Materials Available There are several ASCII files located in the /ftp/biblio area. These contain: (A) A complete description of the Master Bibliography project. (B) A time-stamped list of the materials currently available. (C) A list of contact addresses for the publishers of the materials in the various bibliographic files. International Journal of Geographical Information Systems All issues from inception of publication thru 1992 - one file containing 177,510 bytes (REFER) or 199,168 bytes (PC EndNote) Current (1993) issues: each issue is in a separate file with the first issue of 1993 designated as IJGIS_A.REF or IJGIS_A.LIB, the second as IJGIS_B, etc. There will be at total of six issues in 1993. International Journal of Remote Sensing Selected articles relating to GIS starting with 1993: each issue (one or more articles) is in a separate file with the first issue of 1993 designated as IJRS_A.REF or IJRS_A.LIB, the second as IJRS_B, etc. NOTE: not all issues contain GIS-related articles! International Symposia on Spatial Data Handling (IGU Commission on GIS) 1984 thru 1992 (First thru Fifth Symposia) - separate files 1984 - 40,861 bytes (REFER) or 60,928 bytes (PC EndNote) 1986 - 56,325 bytes (REFER) or 73,728 bytes (PC EndNote) 1988 - 33,556 bytes (REFER) or 53,248 bytes (PC EndNote) 1990 - 116,554 bytes (REFER) or 155,136 bytes (PC End- Note) 1992- 84,661 bytes (REFER) or 105,472 bytes (PC EndNote) Urban & Regional Information Systems Association 1992 Annual Conference Proceedings: one file containing 126,260 bytes (REFER) or 165,888 bytes (PC EndNote) 1993 Annual Conference Proceedings: one file containing 72,853 bytes (REFER) or 99,840 bytes (PC EndNote) ******** Obtaining Copies of Current Files via Anonymous FTP Access to current files is available via anonymous FTP for those individuals and organizations having access to the Internet. Because of copyright restrictions, files will be restricted to those instances where formal agreements have been signed with the publishers. To access the currently available files enter the following commands: ftp 128.146.209.34 (this is BASTET@SBS.OHIO-STATE.EDU) when you are asked to log in, respond with the user name of anonymous when you are asked for a password, please respond with your Internet address. When the log on operation is completed, change to the appropriate directory by using one of the following commands: cd biblio (this places you in the base direc- tory for the project -- several ASCII information files are located here) cd /biblio/gis.refer (this places you in a directory with files in REFER (ASCII) format) cd /biblio/gis.pc (this places you in a directory with files in EndNote format for the PC) NOTE: Mac versions of the EndNote libraries will be available shortly. cd /biblio/gis.mac (this places you in a directory with files in EndNote format for the Mac) You may now copy any of the available files. For example, to copy the ASCII bibliographic entries for the 1992 Spatial Data Handling Symposium select the gis.refer directory and issue the command: get sdh92.refer FTP also supports the command mget which permits the retrieval of multiple files using wild card specifications. For example to retrieve all of the ASCII files dealing with the various Spatial Data Handling Symposia, select the gis.refer directory and issue the command: mget sdh*.* If you are planning to copy either the PC or Mac versions of the EndNote binary files, you must issue the following command before issuing the command to get a copy of the desired file- binary After the file(s) have been copied, they should reside in your default directory on your home machine. To leave the FTP session, issue the final command: quit The master bibliography is searchable at the URL http://thoth.sbs.ohio-state.edu/ ______________________________________________________________________ Q3.1: What are the United States map accuracy standards? From: rcw@scicom.AlphaCDC.COM (Robert White) United States National Map Accuracy Standards With a view to the utmost economy and expedition in producing maps which fulfill not only the broad needs for standard or principal maps, but also the reasonable particular needs of individual agencies, standards of accuracy for published maps are defined as follows: 1. Horizontal Accuracy. For maps on publication scales larger than 1:20,000, not more than 10 percent of the points tested shall be in error by more than 1/30 inch, measured on the publication scale; for maps on publication scales of 1:20,000 or smaller, 1/50 inch. These limits of accuracy shall apply in all cases to positions of well- defined points only. Well-defined points are those that are easily visible or recoverable on the ground, such as the following: monuments or markers, such as bench marks, property boundary monuments, intersections of roads, railroads, etc.; corners of large buildings or structures (or center points of small buildings); etc. In general what is well defined will also be determined by what is plottable on the scale of the map with 1/100 inch. Thus while the intersection of two road or property lines meeting at right angles would come within a sensible interpretation, identification of the intersection of such lines meeting at an acute angle would obviously not be practicable within 1/100 inch. Similarly, features not identifiable upon the ground within close limits are not to be considered as test points within the limits quoted, even though their positions may be scaled closely upon the map. In this class would come timber lines, soil boundaries, etc. 2. Vertical Accuracy, as applied to contour maps on all publication scales, shall be such that not more than 10 percent of the elevations tested shall be in error more than one-half the contour interval. In checking elevations taken from the map, the apparent vertical error may be decreased by assuming a horizontal displacement within the permissible horizontal error for a map of that scale. 3. The accuracy of any map may be tested by comparing the positions of points whose locations or elevations are shown upon it with corresponding positions as determined by surveys of a higher accuracy. Tests shall be made by the producing agency, which shall also determine which of its maps are to be tested, and the extent of such testing. 4. Published maps meeting these accuracy requirements shall note this fact on their legends, as follows: "This map complies with National Map Accuracy Standards." 5. Published maps whose errors exceed those afore stated shall omit from their legends all mention of standard accuracy. 6. When a published map is a considerable enlargement of a map drawing (manuscript) or of a published map, that fact shall be stated in the legend. For example, "This map is an enlargement of a 1:20,000-scale map drawing," or "This map is an enlargement of a 1:24,000-scale published map." 7. To facilitate ready interchange and use of basic information for map construction among all federal map making agencies, manuscript maps and published maps, wherever economically feasible and consistent with the uses to which the map is to be put, shall conform to latitude and longitude boundaries, being 15 minutes of latitude and longitude, or 7.5 minutes or 3-3/4 minutes in size. US Bureau of the Budget Issued June 10, 1941 Revised April 26, 1943 Revised June 17, 1947 ______________________________________________________________________ Q3.2: What is the Vector Product Format and where can I get information? From: tjmisek@hou.amoco.com (Thomas Misek) The document that lists the format & form of the Vector Product Format is: Military Standard MIL-STD-600006 30 September 1993 This 200+ page document has a complete description of the format. [old address deleted - new address from newcomb@navo.navy.mil (Donald R. Newcomb)] The correct address for the public to request any MIL-STD is: Naval Publications & Forms Center Code 3051 5801 Tabot Ave. Philadelphia, PA 19120 Phone: (215) 697-2000 This is DoD's central supply house for MIL-STDs. They are, by the way, all free to US addresses. [original article continues] Since the VPF has been created as a means for transmitting digital geographic databases, I, for one, would be interested in any programs that make use of the format. ______________________________________________________________________ Q3.3: What is this SDTS thing and is it available via ftp? From: "Dan Henke" <dhenke@mercury.er.usgs.gov> Spatial Data Transfer Standard (SDTS) is a standard which by definition is " a document that specifies a set of rules". The SDTS provides a way of facilitating the transfer of digital spatial data between dissimilar computer systems. It also preserves the information meaning and minimizes the need for any external information. This standard not only allows the transfer of spatial data, attributes and georeferencing but also the data quality report, data dictionary and any other associated metadata. Promoting and facilitating the transfer of spatial data between dissimilar computer systems provides users and producers of spatial data with a way to gain access to a greater amount of otherwise inaccessable data. It also promotes data exchange and data sharing, which in turn increase the quality and the integrity of existing spatial data. SDTS is designed to support all types of spatial data. A single translator that could support all the different types and options of data is probably not practical. It is much better to implement SDTS through the use of profiles. A profile is a subset of SDTS which was created to transfer a specific type of spatial data with as few SDTS options as possible. The Topological Vector Profile (TVP) was the first developed and applies to geographic vector data with planar graph topology. This profile will handle both USGS DLG-3 and DLG-F data as well as the Census Bureau's TIGER data. The Raster Profile was developed to accomodate image data, digital terrain models,gridded GIS layers, and other gridded data. This profile will accomodate USGS DEM's and DOQ's. SDTS was approved as Federal Information Processing Standard (FIPS) Publication 173 in 1992 after 12 years of development and testing and in 1994 became mandatory for federal agencies. SDTS is available for use also by state and local goverments, the private sector and research and academic organizations. SDTS information including the Standard itself and much more is available via ftp at: ftp://sdts.er.usgs.gov/pub/sdts More information on SDTS is also available by visiting the SDTS web page located at: http://mcmcweb.er.usgs.gov/sdts/ You may also write : SDTS Task Force U. S. Geological Survey 1400 Independence Road Rolla, MO. 65401 or Call 573/308-3543, FAX 573/308-3652 or e-mail : sdts@usgs.gov ______________________________________________________________________ Q3.4: What is a DXF file and where can I get info about it? From: tchild@AUTODESK.COM (Timothy Child) DXF(R) is the Drawing eXchange Format from AutoCAD. The definitive documentation for this format is in the current AutoCAD Release 12 Customization Manual. I believe that a copy of the DXF appendix is also posted on the Autodesk Compuserve forum. Try contacting the Autodesk Australian office for details on this: 9 Clifton St. P.O. Box 458 Richmond Victoria 3121 Phone 429-9888 Another good reference for the DXF format is provided in: The AutoCAD Database Book Authors: F.H. Jones and L. Martin Published by Ventana Press ISBN 0-940087-04-9 Ventana Press may be contacted at: P.O. Box 2468 Chapel Hill NC 27515 USA Phone (919) 490-0062 Also, Virginia Hetrick, in sunny Calififornia <IARGRAF@MVS.OAC.UCLA.EDU> suggests: Kay, David C., and John R. Levine (1992) Graphics File Formats. Sorry, I don't know either the ISBN number or the publisher since I just got an ad with the book identified in it and it specifically says that it contains a description of DXF formats. I'd suspect that this one is probably more readily available in libraries than the others. WWW resources: A page of links: http://wwwis.cs.utwente.nl:8080/faase/DWG/dxf.html Release 13 documentation in Windows Help format with a supplementary browser to simplify searching: http://www.cloudnet.com/~dyoung/ Release 10 documentation in text format: ftp://ftp.cc.monash.edu.au/pub/graphics.formats/DXF.ascii.Z _______________________________________________________________________ Q3.5: What is DEM? From: David Mark (dmark@sun.acsu.buffalo.edu) The terminology in this area is somewhat complicated. The U.S. Geological Survey does indeed have a 'product' that is called "Digital Elevation Model". These are gridded elevation data, 30 m resolution. Standard data sets cover 7.5 minute by 7.5 minute areas equivalent to USGS 1:24,000 scale maps. The USGS has another data-set series called "Digital Terrain Models", most or all of which were originally developed by the US Army and/or Defense Mapping agency, from 1:250,000 scale maps. Outside of USGS, there is some disagrement in the literature as to whether "Digital Elevation Model" (DEM) is a _generic_ term for all digital data for elevations, including TINs, digitized contours, etc., or whether the DEM term should be restricted to regular rectangular grids. Those who prefer to restrict the term DEM to grids often prefer to use "Digital Terrain Model" (DTM) as the _generic_ term for all computerized elevation data. Bruce Gittings maintains a Digital Elevation Data catalogue, which is posted monthly on GIS-L. This catalogue, which is regularly updated, contains descriptions of a large number of topographic and bathymetric datasets with local, regional and global extent. There are also useful references to a number of other types of data (eg. USGS products, Digital Chart of the World, regional databases for Asia, Europe etc.). It is well worth checking this list before looking elsewhere for data. The most up-to-date version of this catalogue is available through the Edinburgh GIS WWW server. WWW URL: http://www.geo.ed.ac.uk/home/ded.html The catalogue is also available through a mail server. Send e-mail to geoinfo@geovax.edinburgh.ac.uk for full details of how to use this service. DEMs are available from spectrum.xerox.com [192.70.225.78], /pub/map Contact: Lee Moore -- Webster Research Center, Xerox Corp. Voice: +1 (716) 422 2496 Arpa, Internet: Moore.Wbst128@Xerox.Com For information on converting DEM to ARCVIEW format, see http://www7440.nrlssc.navy.mil/muse.html _______________________________________________________________ Q3.6: Where can I get information about TIGER/Line? I heard there is a terrific new and improved release... :-) For information on TIGER/Line products and releases, call the US Census Bureau at 301-457-4100 Call particular vendors for TIGER to vendor-format conversion problems. Also, get TIGER information on the WWW at: http://www.census.gov/geo/www/tiger/ And while we're on the subject of Census Data.... From: Henk Meij <hmeij@ciesin.org> A data archive was created and is maintained by the National Aeronautics and Space Administration (NASA), under GSFC Letter Contract NAS5-32632, by the Socioeconomic Data and Applications Center (SEDAC) of the Consortium for International Earth Science Information Network (CIESIN) in cooperation with the Urban Information Center (UIC) at the University of Missouri St. Louis. The archive contains boundary files based on 1992 TIGER/Line, standard extract files based on 1990 STF3A, Block statistics from STF1B, and enhanced migration files based on STP28, county to county. This is alla vailable at: ftp ftp.ciesin.org <login in as "ftp" or "anonymous"> <send email address as password> cd /pub/census o helpful readme files will be displayed to the screen o documentation, albeit still sparse, online o all files in (binary) zipped archive-file format (use ftp mode BINARY for retrieval) o unzip binaries for many platforms provided as well as unzip/zip source code _______________________________________________________________ Q3.7: How do I order USGS maps? It's easy. Just call (in the US) 1-800-USA-MAPS _______________________________________________________________ Q3.8: What is the Digital Chart of the World (DCW) and how do I get one? From: Mike Phoenix <esri!mailgate_esri!mike_phoenix@UUNET.UU.NET> The Digital Chart of the World is a 1.7 GB digital geographic database that is available on CD-ROM. It was input from 1:1,000,000 Operational Navigation Charts and 1:2,000,000 Joint Navigation Charts. It includes 17 layers, aeronautical info, data quality info, drainage, supplemental drainage, hypsography, hypsography supplemental, land cover, ocean features, physiography, political/ocean, populated places, railroads, transportation structure, utilities, and vegetation. It is ISO9660 compatible and only $200.00. It is available from: For civilian customers only (military users have a different set of contacts in each of the four regions). In the US, Latin America, Asia, and Africa: U.S. Geological Survey ESIC-Open File Section Box 25286 Federal Center Mail Stop 517 Denver, CO 80225, USA Tel. (303) 202-4200 <-- new number In Canada Products and Services Division Surveys, Mapping, and Remote Sensing Sector Energy, Mines and Resources Canada 615 Booth Street, Room 400 Ottawa, Ontario, CANADA K1A 0E4 Tel. (613) 995-2123 Fax. (613) 995-6001 In Europe Chadwyck-Healey Ltd. Cambridge Place Cambridge CB2 INR UNITED KINGDOM Tel. (0223) 311479 Fax. (0223) 66440 In Australia The Manager AUSMAP Data Unit P.O. Box 2 BELCONNEN ACT 2617 AUSTRALIA Sindre Langaas <SINDRE@system.ecology.su.se> has more info at http://ilm425.nlh.no/gis/dcw/dcw.html From: karl@grebyn.com (Karl A. Nyberg) Payment (check, money order, purchase order, or Government account) must accompany order. Make all drafts payable to the Department of the Interior -- U. S. Geological Survey. The DCW package can also be purchased over-the-counter from any Earth Science Information Center [ESIC] by check, money order, purchase order, Government account, credit card, or cash. Missing or defective material will be replaced free if reported to the office that took the order, by telephone or in writing, within 90 days of purchase. Cost $200 per package. Includes 4 CD ROMs, 3 5.25 and 3.5 floppies containing various source and executable files for VPFVIEW, a program for displaying the data on the PC. You need DOS 3.1 or higher, CD-ROM Extensions 2.0 or higher. 80[23]86 with 80[23]87, VGA or EGA and arrow key, mouse, 30MB hard drive with at least 20 percent free 1MB RAM, CD ROM drive. I was told that the FASTEST way was to order it from Denver. I sent in my check on 8/21 and received the package today from UPS. I believe that DoD components can order directly from DMA, although I don't know how. That information is probably classified, and I don't have either a clearance OR a need to know. :-) There's apparently also a version of VPFVIEW in process for the Sun SPARC, with public availability estimated to be within the next couple months. (That's what I'm looking forward to!) The DCW is also available as an Arc/Info coverage. See http://www.esri.com/base/data/catalog/esri/esri_dcw.htm for more info. ______________________________________________________________________ Q3.9 Is there a package available to convert FROM UTM to latitude/longitude? An on-line service is available at: http://www.geod.nrcan.gc.ca/html-public/GSDapps/English/gsrug-gtou.html The Geographic Calculator Resolution Mapping, Inc., River Road, P.O. Box 718, Newcastle, ME 04553. (207) 563-2311. The GC is a Microsoft Windows application that enables conversion to-from Lat/Long, State Plane, UTM, Landsat WRS, user defined coordinate and other systems. It sells for $225. This is a solution if you don't have something like Arc/Info, in which these CONVERTsions are standard fare. Geocart Terra Data, Inc (Bramblebush, Croton-on-Hudson, NY 10520) (212 675-2971). it does map projections; Mac based; $499. PROJ4 PROJ is a standard Unix filter function which converts geographic longitude and latitude coordinates into cartesian coordinates, (lambda,phi) -> (x,y), by means of a wide variety of cartographic projection functions. For many of the projection functions the inverse conversion, (x,y) -> (lambda,phi), can also be performed." The Unix version of the software (buildable with gcc) and PC-DOS version of the software (both executable & source) are located in ftp://kai.er.usgs.gov/pub/PROJ.4 This software supports a *very* robust set of coordinate projection systems, datums, and ellipsoids. This software is especially useful if you have to convert large batches of coordinates. GeoConverter ($5.00 shareware) This software does accurate conversions between UTM and Long/Lat for Macintosh computers. ftp://ftp.utexas.edu/pub/mac/da/geo-converter-11.hqx ______________________________________________________________________ Q3.10: Does a file exists of latitude and longitude of US cities? From: Craig Best <cbest@census.gov> Yes, the Census Bureau has such a beast at ftp://ftp.census.gov/pub/tiger/points/geoex.exe This is a self-extracting file containing 51 dbf files, one for each state and DC. ______________________________________________________________________ Q3.11: Where can I get old antique maps? Contact the International Map Dealers Association. Norman Strasma is the Executive V.P., and their offices are in Kankakee, Il (PO Box 1789, Zip=60901-1789, phone 815-939-4627) Library of Congress Also, try local libraries [Ed. note: I got a *great* map of Buffalo from 1854 at the Erie County Public Library. It's an old insurance map with building types denoted.]. ______________________________________________________________________ Q3.12: Is there a standard for representing latitude and longitude? Yes. ISO 6709:1983 Standard Representation of Latitude, Longitude and Altitude for Geographic Point Locations. ______________________________________________________________________ Q3.13: Has anyone compiled a list of standards and formats? Yes, people are attempting to do this. For a start, check out: http://www.ru/gisa/english/cssitr/format/index.htm ______________________________________________________________________ Q4.1: What are some other related mailing lists, ftp sites and internet sources for useful resources? A. Bill Thoen has compiled a *huge* resource list titled "On-line Resources Earth Sciences". This list is very detailed and well organized. It is a valuable addition to any library and is available at: ftp://ftp.csn.org/COGS/ores.txt http://www.csn.net/~bthoen/ores/ Also, see Bill's articles in the Feb and August 1994 GIS World. ______________________________________________________________________ Q4.2: How do I subscribe to GIS-L? If you are unable to access the comp.infosystems.gis newsgroup, you can see the same discussion by subscribing to GIS-L. Send the one line message: subscribe GIS-L <your_name> to LISTSERVER@URISA.ORG. Items to be distributed to the list should be sent to GIS-L@URISA.ORG or posted to comp.infosystems.gis. ESRI-L? To Subscribe to ESRI-L: Send message to: "esri-l-request@esri.com". In the subject line of the message, type the word: "subscribe" To Unsubscribe from ESRI-L: Send message to: "esri-l-request@esri.com". In the subject line of the message, type the word: "unsubscribe" And ai-geostats? To subscribe to ai-geostats, send the following in the body (not the subject line) of an email message to "Majordomo@gis.psu.edu": subscribe ai-geostats This will subscribe the account from which you send the message to the ai-geostats list. ai-geostats-digest also exists. Send mail to ai-geostats-digest-request@gis.psu.edu to get the info. ______________________________________________________________________ Q4.3: What are some books and magazines available on GIS? ____ GeoInfo Systems Magazine, PO Box 7678, Riverton, NJ 08077-9178 $59/year. Email: geoinfomag@aol.com ____ GIS World and Business Geographics magazines, and the 199x GIS Sourcebook, all from GIS World Inc, 155 E Boardwalk Drive, Suite 250, Fort Collins, CO 80525. Email: info@gisworld.com ____ Proceedings: 5th International Symposium on Spatial $50.00 Data Handling. IGU Commission on GIS, August 1992, Charleston, South Carolina. Two volume set contains more than seventy selected papers representing the state of the art in geographical information processing. ____ Time in Geographic Information Systems, by Gail Langran. $40.00 Taylor & Francis, 1992. Thorough examination of the conceptual, logical, and physical design of temporal GISs. This book reviews the literature; discusses implementation issues such as clustering, quality control, and volume control; and introduces original and previously unpublished research on the extension of existing spatial data structuring techniques to a three-dimensional space-time application. ____ Accuracy of Spatial Databases, edited by Michael Goodchild. $77.00 Taylor & Francis, 1989. Detailed treatment of error and accuracy, particularly of modelling uncertainty and reliability, testing accuracy, and the practical implications for use of spatial data. ____ An Album of Map Projections, U.S.G.S. Professional Paper 1453, John Snyder and Philip Voxland, 1989. ____ Analytical and Computer Cartography, by Keith Clarke. $52.00 Prentice Hall, 1990. ____ Applications of Spatial Data Structures, by Hanan Samet. $45.25 Addison-Wesley, 1989. Applications of hierarchical data structures in computer graphics,image processing, and GIS. ____ Building Databases for Global Science, edited by Helen $93.00 Mounsey. General Editor: Roger Tomlinson. Taylor & Francis, 1988. Papers from the first meeting of the International Geographical Union's Global Database Planning Project. ____ Design and Analysis of Spatial Data Structures, by $43.25 Hanan Samet. Addison-Wesley, 1990. Hierarchical (quadtree and octree) data structures. ____ Fundamentals of Geographic Information Systems: A $60.00 Compendium. ACSM, 1990. ____ Fundamentals of Spatial Information Systems $49.95 Robert Laurini and Derek Thompson Academic Press, London, UK 1992, 700 pages approx., ISBN 0-12-438380-7. (Particularly nice illustartions ;-)) ____ Geographic and Land Information Systems for $45.00 Practicing Surveyors: a Compendium. ACSM, 1991. ____ Geographic Information Systems: A Management $57.00 Perspective, by Stan Aronoff. WDL Publications, 1989. An excellent introduction to GIS principles and applications for users and managers. ____ Geographic Information Systems: An Introduction, by $51.00 Jeffrey Star and John Estes. Prentice Hall, 1990. Introductory textbook for students and professionals. ____ Geographic Information Systems and Cartographic $51.00 Modelling, by Dana Tomlin. Prentice Hall, 1990. Introduction to cartographic modelling, emphasizing environmental decisions, that develops a high-level cartographic computing language. ____ Geographic Information Systems for Resource $60.00 Management, edited by William Ripple. ACSM, 1986. Papers on land suitability; water, soil, and vegetation resource management; and urban and global GIS applications. ____ Geographical Information Systems: Principles and $295.00 Applications, edited by David J. Maguire, Michael F. Goodchild and David W. Rhind. John Wiley & Sons, 1991. Two-volume boxed set contains sixty new papers; the most ambitious, extensive, and authoritative GIS book to date. ____ The Geography Coloring Book, by Wynn Kapit $10.00 Harper Collins, 1991. A creative and expert study aid for learning geography. Contains coloring plates and index. ____ The Global Positioning System and GIS, by Michael Kennedy An educational tool intended as an introduction for all mapping science professionals, managers, and students. For use in the classroom, or as a self-teaching guidebook, "GPS and GIS" explains how GPS works, examines software and hardware options, and provides theory to application in a manual. Ann Arbor Press ISBN 1-57504-017-4 ____ Handbook of Relational Database Design, by Candace $46.00 Fleming and Barbara von Halle. Addison-Wesley, 1989. This book provides a practical approach to designing relational databases. It contains two complementary design methodologies: logical data modeling and relational database design. The methodologies are independent of product-specific implementations and have been applied to numerous relational product environments. ____ (workbook). UGC Corporation, 1990. Management-level primer on GIS with accompanying video. [Ed. note: at one time this was offered without the video free of charge] ____ How to Choose A GIS Consultant, available free from EI Technologies, LLC, 2620 S. Parker Road, Ste. 150, Aurora, CO 80014. ____ Interpreting Space: GIS and Archaeology, edited by $79.00 Kathleen M. S. Allen, Stanton W. Green and Ezra B. W. Zubrow. Taylor & Francis, 1990. The first book to address the use of GIS in archaeology and anthropology. ____ Introduction to Database Systems, Vol I, by C. J. Date. $46.25 Fifth edition. Addison-Wesley, 1990. ____ Introduction to Database Systems, Vol II, by C. J. Date. $45.25 Addison-Wesley, 1985. ____ Introduction to Urban GIS, by William Huxhold (paper). $32.50 Oxford University Press, 1991. ____ Introductory Readings in Geographic Information $39.00 Systems, edited by Donna Pequet and Duane Marble. (paper). Taylor & Francis, 1990. Selection of articles on various aspects of GIS. ____ Map Appreciation, by Mark Monmonier. $41.00 Prentice Hall, 1988. Teaches how to work with maps and promotes graphic literacy. ____ Map Generalization: Making Rules for Knowledge $95.00 Representation, edited by Barbara Buttenfield and Robert McMaster. John Wiley & Sons, 1991. This book is the first to focus on the development of a rule base for digital mapping. It identifies the problems involved in the development of a rule base for digital maps used in GIS, and it provides a framework to help solve these problems, improve efficiency, preserve consistency, and incorporate sound principles into digital mapping. ____ Mapping the Next Millenium: The Discovery of New $30.00 Geographies, by Stephen Hall Random House, 1992. Contains reports from the scientific frontiers where virtually every aspect of the physical cosmos is being mapped, including the floor of the ocean, the hole in the ozone layer, the interior of the earth, atoms and chromosomes, the farthest planets of the solar system, the large-scale structure of the universe, and even the mathematical construct known as pi. _____ Map Projections---A Working Manual. USGS Professional Paper 1395. by John Snyder. $32. Available from USGS Distribution Center, Box 25286, MS 306, Denver Federal Center, Denver, CO 80225. ____ Principles of Geographical Information Systems for $44.00 Land Resources Assessment, by P. A. Burrough. Oxford University Press, 1986. Textbook for more advanced GIS specialists. ____ Reactive Data Structures for Geographic Information Systems, Peter van Oosterom 1994 Oxford University Press, ISBN 0-19-823320-5. This 200-page book is part of the "Spatial Information Systems" series of Oxford University Press (General Editors: P.H.T. Beckett,P.A. Burrough, M.F. Goodchild, and P. Switzer). The full price of the book is 25 pounds. In addition to an overview of GIS-technology this book contains many recent research results. This is illustrated with many figures (80) and references (296) and easy accessible by an index with 872 entries. ____ Statistics for Spatial Data, by Noel Cressie. $90.00 John Wiley & Sons, 1991. The most comprehensive and readable text to date on the analysis of spatial data through statistical models. It unifies a previously disparate subject under a common approach and notation. ____ Three Dimensional Applications in Geographic Information $66.00 Systems, edited by Jonathan Raper. Taylor & Francis, 1989. Survey of approaches and problems in modelling real geophysical data. _______________________________________________________________________ Q4.4: Where can I get a copy of the SpatioTemporal Bibliography? From: soo@CS.ARIZONA.EDU (Michael Soo) If you would like a copy of the document or the database and do not have ftp access, we ask that you first try the ftpmail facility available on cs.arizona.edu. Simply send an e-mail message to ftpmail@cs.arizona.edu that contains the ftp commands needed to retrieve the desired files. The subject line of the message is irrelevant. For example, to retrieve both the postscript bibliography and the bibliographic database, the body of the message should contain the following. open cd bib get spacetime.bib get spacetime.ps The files will be mailed back to you, divided into chunks that can be glued together with the help of your favorite editor. ____________________________________________________________________ Q4.5: What are some professional organizations out there for GISers? URISA is the Urban and Regional Information Systems Assn 900 Second St. NE, Ste 304 Washington, DC 20002 (202) 289-1685 Email: urisa@macc.wisc.edu URISA is a large organization of primarily governmental interest folks that use information systems in general, and it has a large element of GIS interests included in that. They hold a large national conference, publish a journal, and distribute periodic newsletters, including one devoted exclusively to GIS job listings (URISA Marketplace). AM/FM International 14456 E. Evans Ave Aurora, CO 80014 (303) 337-0513 AM/FM-I is another fairly large organization that deals largely with GIS applications in facilities management and utilities-related mapping. It also hosts an annual conference, publishes a newsletter, and provides educational support through scholarships and internships. ---Martin D. Crossland Computer Information Systems Dept AAG is the Association of American Geographers, the address is 1710 Sixteenth St NW, Washington, DC 20009-3198 USA. http://www.aag.org. Voice (202) 234-1450, FAX: (202) 234-2744 E-Mail: gaia@aag.org. Membership: member@aag.org _____________________________________________________________________ Q4.6: What are some journals which carry GIS articles? From: Casson Stallings and Friends <cass@nrrc.ncsu.edu> GIS Journals: Annals of the Association of American Geographers Business Geographics (business) Cartographica Cartography and GIS Computer (algorithms and visualization) Computers, Environment, and Urban Systems Computers and Geoscience GrassClippings IEEE Trans. on Comp. Graphics and Applications (visualizaiton) International Journal of GIS Photogrammetric Engineering and Remote Sensing Journals that carry some GIS articles: Geocarto IEEE Geosciences International Journal of Remote Sensing Landscape Ecology Remote Sensing Review _____________________________________________________________________ Q4.7: How can I subscribe to the Int'l Journal of GIS? From: Duane F. Marble <dmarble@magnus.acs.ohio-state.edu> http://www.tandf.co.uk Editor: Dr. Peter F. Fisher Midlands Regional Research Laboratory Department of Geography University of Leicester Leicester, LE1 7RH UNITED KINGDOM Telephone: 44-0533-523839 Fax: 44-0533-523854 Email: pff1@leicester.ac.uk North American Editor: Dr. Keith Clarke Department of Geology and Geography Hunter College City University of New York 695 Park Avenue New York, NY 10021 Telephone: 212-772-5265 Fax: 212-772-5268 Email: kclarke@everest.hunter.cuny.edu SUBSCRIPTIONS Online or Print Version (GISO): Institutional: US$510 Personal: US$239 (print only) Online and Print Version (GISOP): Institutional: US$612 United States, Canada, and Mexico Subscriptions: Taylor & Francis, Inc. 1900 Frost Road, Suite 101 Bristol, PA 19007 Australia Subscriptions: R. Hill & Son Ltd. 119 Gardenvale Road, Suite 2 Gardenvale, Victoria 3185 New Zealand Subscriptions: R. Hill & Son Ltd. Private Bag Newmarket Auckland 1 India Subscriptions: Universal Subscription Agency Pvt. Ltd. 101-102 Community Centre Malviya Nagar Extn Post Bag No. 8 Saket New Delhi 110017 Japan Subscriptions: Kinokuniya Company Ltd. Journal Department P.O. Box 55 Chitose Tokyo 156 _____________________________________________________________________ Q4.8: What are some World Wide Web URLs for GIS information? [Ed. Note 2/13/97: It's a waste of space to keep a list of URLs here so from now on I'll only list a few good jump sites.] Yahoo! GIS Page http://www.yahoo.com/Science/Geography/ Geographic_Information_Systems__GIS_/ Jim Aylward's Great GIS Net Sites http://www.hdm.com/gis3.htm Paul Leunissen's GIS*Links http://web.idirect.com/~pleuniss/links.html _____________________________________________________________________ Q4.9 Where can I find pointers to satellite data? One site is SOEST SATELLITE OCEANOGRAPHY LABORATORY: http://satftp.soest.hawaii.edu _____________________________________________________________________ Q4.10: Are any mailing lists archived anywhere? ESRI-L, ARCVIEW-L and IMAGRS-L are archives at: http://www.gis.umn.edu/rsgisinfo/lists.html or gopher://gopher.gis.umn.edu/11/rsgis/lists/ To Get ESRI-L Archives: For a list of all the ESRI-L archive server commands, send a message with "archive" in the subject line and "help" in the body to "esri-l-request@esri.com". You will receive a document that explains how to search and retrieve the ESRI-L archives. ai-geostats is archives at: ftp://gis.psu.edu/pub/ai-geostats/ _____________________________________________________________________ Q4.11: Can you recommend any other resource documents? The Virtual Earth - A Tour of the WWW for Earth Scientists http://atlas.es.mq.edu.au/users/pingram/v_earth.html _____________________________________________________________________ Q4.12: Can you point me towards some on-line job resources? Sure we can. Use your favorite WWW browser to access: The GIS Jobs Clearinghouse http://www.gis.umn.edu/rsgisinfo/jobs.html The Geosci Jobs Archive http://www.eskimo.com/~tcsmith/mail/gsj-arc.html _____________________________________________________________________ Q5.1: What is the best way to calculate the great circle distance (which deliberately ignores elevation differences) between 2 points? (This answer was prepared by Robert G. Chamberlain of Caltech (JPL): rgc@solstice.jpl.nasa.gov and reviewed on the comp.infosystems.gis newsgroup in Oct 1996.) If the distance is less than about 20 km (12 mi) and the locations of the two points in Cartesian coordinates are X1,Y1 and X2,Y2 then the Pythagorean Theorem d = sqrt((X2 - X1)^2 + (Y2 - Y1)^2) will result in an error of less than 30 meters (100 ft) for latitudes less than 70 degrees less than 20 meters ( 66 ft) for latitudes less than 50 degrees less than 9 meters ( 30 ft) for latitudes less than 30 degrees (These error statements reflect both the convergence of the meridians and the curvature of the parallels.) The flat-Earth distance d will be expressed in the same units as the coordinates. If the locations are not already in Cartesian coordinates, the computational cost of converting from spherical coordinates and then using the flat-Earth model may exceed that of using the more accurate spherical model. Otherwise, presuming a spherical Earth with radius R (see below), and the locations of the two points in spherical coordinates (longitude and latitude) are lon1,lat1 and lon2,lat2 then the Haversine Formula (from R.W. Sinnott, "Virtues of the Haversine", Sky and Telescope, vol. 68, no. 2, 1984, p. 159): dlon = lon2 - lon1 dlat = lat2 - lat1 a = sin^2(dlat/2) + cos(lat1) * cos(lat2) * sin^2(dlon/2) c = 2 * arcsin(min(1,sqrt(a))) d = R * c will give mathematically and computationally exact results. The intermediate result c is the great circle distance in radians. The great circle distance d will be in the same units as R. The min() function protects against possible roundoff errors that could sabotage computation of the arcsine if the two points are very nearly antipodal (that is, on opposide sides of the Earth). Under these conditions, the Haversine Formula is ill-conditioned (see the discussion below), but the error, perhaps as large as 2 km (1 mi), is in the context of a distance near 20,000 km (12,000 mi). Most computers require the arguments of trignometric functions to be expressed in radians. To convert lon1,lat1 and lon2,lat2 from degrees, minutes, and seconds to radians, first convert them to decimal degrees. To convert decimal degrees to radians, multiply the number of degrees by pi/180 = 0.017453293 radians/degree. Inverse trigonometric functions return results expressed in radians. To express c in decimal degrees, multiply the number of radians by 180/pi = 57.295780 degrees/radian. (But be sure to multiply the number of RADIANS by R to get d.) The problem of determining the great circle distance on a sphere has been around for hundreds of years, as have both the Law of Cosines solution (given below but not recommended) and the Haversine Formula. Sinnott gets the credit here because he was quoted by Snyder (cited below). Perhaps someone will provide the truly seminal reference so the proper attribution can be given? The Pythagorean flat-Earth approximation assumes that meridians are parallel, that the parallels of latitude are negligibly different from great circles, and that great circles are negligibly different from straight lines. Close to the poles, the parallels of latitude are not only shorter than great circles, but indispensably curved. Taking this into account leads to the use of polar coordinates and the planar law of cosines for computing short distances near the poles: The Polar Coordinate Flat-Earth Formula a = pi/2 - lat1 b = pi/2 - lat2 c = sqrt(a^2 + b^2 - 2 * a * b * cos(lon2 - lon1) d = R * c will give smaller maximum errors than the Pythagorean Theorem for higher latitudes and greater distances. (The maximum errors, which depend upon azimuth in addition to separation distance, are equal at 80 degrees latitude when the separation is 33 km (20 mi), 82 degrees at 18 km (11 mi), 84 degrees at 9 km (5.4 mi).) But even at 88 degrees the polar error can be as large as 20 meters (66 ft) when the distance between the points is 20 km (12 mi). The latitudes lat1 and lat2 must be expressed in radians (see above); pi/2 = 1.5707963. Again, the intermediate result c is the distance in radians and the distance d is in the same units as R. An UNRELIABLE way to calculate distance on a spherical Earth is the Law of Cosines for Spherical Trigonometry ** NOT RECOMMENDED ** a = sin(lat1) * sin(lat2) b = cos(lat1) * cos(lat2) * cos(lon2 - lon1) c = arccos(a + b) d = R * c Although this formula is mathematically exact, it is unreliable for small distances because the inverse cosine is ill-conditioned. Sinnott (in the article cited above) offers the following table to illustrate the point: cos (5 degrees) = 0.996194698 cos (1 degree) = 0.999847695 cos (1 minute) = 0.9999999577 cos (1 second) = 0.9999999999882 cos (0.05 sec) = 0.999999999999971 A computer carrying seven significant figures cannot distinguish the cosines of any distances smaller than about one minute of arc. The function min(1,(a + b)) could replace (a + b) as the argument for the inverse cosine for the same reason as in Sinnott's Formula, but doing so would "polish a cannonball". 5.1a: What value should I use for the radius of the Earth, R? The historical definition of a "nautical mile" is "one minute of arc of a great circle of the earth". Since the earth is not a perfect sphere, that definition is ambiguous. However, the internationally accepted (SI) value for the length of a nautical mile is (exactly, by definition) 1.852 km or exactly 1.852/1.609344 international miles (that is, approximately 1.15078 miles - either "international" or "U.S. statute"). Thus, the implied "official" circumference is 360 degrees times 60 minutes/degree times 1.852 km/minute = 40003.2 km. The implied radius is the circumference divided by 2 pi: R = 6367 km = 3956 mi The shape of the Earth is well approximated by an oblate spheroid with a polar radius of 6357 km and an equatorial radius of 6378 km. PROVIDED a spherical approximation is satisfactory, any value in that range will do, such as R (in km) = 6378 - 21 * sin(lat) See the WARNING below! R (in mi) = 3963 - 13 * sin(lat) where lat is a latitude near which the bulk of your calculations occur. WARNING: This formula for R gives but a rough approximation to the radius of curvature as a function of latitude. The radius of curvature varies with direction and latitude; according to Snyder ("Map Projections - A Working Manual", by John P. Snyder, U.S. Geological Survey Professional Paper 1395, United States Government Printing Office, Washington DC, 1987, p24), in the plane of the meridian it is given by R' = a * (1 - e^2) / (1 - e^2 * sin^2(lat))^(3/2) where a is the equatorial radius, b is the polar radius, and e is the eccentricity of the ellipsoid = (1 - b^2/a^2)^(1/2). 5.1b: When is it NOT okay to assume the Earth is a sphere? A quick test is: Compute the values of R produced by the equation with the WARNING when you use the highest and lowest latitudes that occur in your analysis. Compare the results produced by using these two values in your analysis. If the different results are different enough to cause you to change your action (or your recommendation, or your interpretation of the implication of the results, etc.), then assuming the Earth is spherical is NOT okay. For most purposes, it is quite satisfactory to treat the Earth as a sphere. If necessary, an ellipsoid can provide a better approximation. Some standard textbooks that may be helpful follow (reviews are by Steve Robertson of Tangent Survey Systems in Canada: stever@mindlink.bc.ca): Bomford, Guy 1980 _Geodesy_ Clarendon Press, Oxford ISBN 0-19-851946-X Review: For geodetic computations, this is pretty well the standard in English. It's a cookbook and offers no development, however. Vanicek, Petr, and Krakiwsky, Edward 1986 _Geodesy, the Concepts_ North-Holland, Amsterdam ISBN 0-444-87775-4 Review: This offers a great, but quite involved, discussion of the concepts behind geometrical (and all other) geodesy. Torge, Wolfgang 1980 _Geodesy_ de Gruyter, Berlin (translated to English by C. Jekeli) ISBN 3-11-007232-7 Review: This concentrates mostly on gravimetric geodesy, but has some geometrical stuff, well explained without too much mathematics. Software for solving distance and azimuth problems on the ellipsoid can be obtained (as of 10/10/96) by anonymous ftp from several sources, two of which are listed below: The URL of the National Geodetic Survey (of the National Oceanic and Atmospheric Administration in the US Department of Commerce) is: ftp://www.ngs.noaa.gov/pub/pcsoft/for_inv.3d/ Review (by Ronald C. McConnell of Bellcore: rcmcc@cc.bellcore.com): They have Fortran source and PC executable versions of both the normal "inverse" great circle calculations (two lat/long pairs to distance and bearing), and the less used "forward" calculation (one lat/long pair plus bearing and distance to the second lat/long pair). They have both 2-dimensional and 3-dimensional versions of each. The inverse program works to within a few seconds or a few minutes, depending on the fortran compiler, of the antipodal points. The forward program seems immune to any and all problem locations and pairs of locations. You can choose among a couple of dozen ellipsoids. See the read.me file for explanations. The NGS software directory may contain other listing of interest. Its URL is: http://www.ngs.noaa.gov/PC_PROD/pc_prod.html/ Case is relevant in many URLs - eg: this one. Another anonymous ftp source for ellipsoid software is the US Geological Survey (of the US Department of the Interior), at: http://kai.er.usgs.gov/ftp/PROJ.4/proj.html Again, see the README file for explanations. The URLs for the USGS directory and home page are: http://kai.er.usgs.gov/ftp/index.html http://kai.er.usgs.gov/homepage.html 5.1c: When is it NOT okay to assume the Earth is an ellipsoid? The shape the Earth would assume if it were all measured at mean sea level is called the geoid. The geoid varies no more than about a hundred meters above or below a well-fitting ellipsoid, a variation far less than the ellipsoid varies from the sphere. Terrain relief is reported relative to the geoid. (Paraphrased from p. 11 of the book by Snyder cited above.) Distances on the surface of the geoid are not particularly meaningful. However, there are applications, such as long-term prediction of orbits of Earth satellites, that require better approximations than are provided by an ellipsoid. Astrodynamics texts, such as Kaula, William M. 1966 _Theory of Satellite Geodesy_ Blaisdell Publishing Co., Waltham, MA (This book may be out of print.) Battin, Richard H. 1964 _Astronautical Guidance_ McGraw-Hill, New York (There may be later editions.) may be consulted for further information. Distances on the surface of the terrain, whether geodesic, on roads, cross-country, or straight-line, depend on relief (including elevation differences), the status of engineering projects, and perhaps even route selection. Hence, computation is idiosyncratic and not well suited to simple approximations. ______________________________________________________________________ Q5.2: What is GPS? More information is available from: http://www.utexas.edu/depts/grg/gcraft/notes/gps/gps.html http://www.einet.net/editors/john-beadles/introgps.htm Richard Langley <lang@unb.ca> maintains a list of GPS informations sources. From: Ed Keller <ewk@icf.hrb.com> Greg Holmberg <greg@surfgear.com> Don Cooke <don_cooke@gdt1.com> GPS consists of three parts: the 24 satellites, a portable receiver, and the control center on Earth. Each satellite carries a computer and a very accurate atomic clock. The control center calculates each satellite's orbit a week or so into the future, predicts ionospheric conditions over that time, and then uploads this information into the satellite's computer. This information is called the "ephemeris". By consulting its clock and the ephemeris, the satellite can tell where it is in the sky at any given microsecond during the week. It transmits its position and the current time continuously. Each receiver has a less accurate clock. When activated, it listens for satellites that are scheduled to be above the horizon each satellite has its own assigned radio frequency).It then subtracts the first received time from the time on its internal clock. This gives a distance, which can be pictured as a sphere around the satellite several hundred miles in diameter. The next signal will define a similar sphere, and the intersection of the two is a circle which passes through the Earth. If the system were ideal, a second time and location signature from another satellite would give a precise triangulation. In reality, three signals are needed simultaneously for latitude and longitude, and a fourth is required for fixing altitude in steps of less than a few hundred feet. The reason for this apparent gross inaccuracy is a DoD policy called "Selective Availablity". he satellites are instructed to "dither" both their times and their locations, that is, they round off their transmissions into less accurate steps. This is done mainly to prevent a foreign military power from using the GPS as a free,super-accurate,preinstalled targeting computer. There are two ways to use GPS to find your position. The first technique (discussed above) gives instant results anywhere with just one receiver. The penalty is the decreased accuracy. You can expect a single receiver GPS-calculated position to be within 100 meters of where a surveyor would place it. The best measurements are made when three satellites are 120 degrees apart around the horizon, and the fourth satellite is directly over- head. If you desire greater accuracy, the arrival time of the signal at the receiver may be compared with that of signals received simultaneously at another location whose exact coordinates are known.The difference between these two sets of data yields a location accurate to within 0.5 to 20 meters, and is known appropriately as "Differential GPS". If you desire even greater accuracy, the underlying carrier wave of the signals can be analyzed after capture, and compared with signals received simultaneously at another known location. The difference between these two sets of data yields a location accurate to within a centimeter. Why does the GPS signal include ionospheric data when timing data would suffice? The ionosphere is a high-altitude layer of the Earth's atmosphere that receives punishing amounts of solar radiation. This radiation ionizes the gases, causing the layer to have varying permeability to radio waves. As the thickness of the ionosphere changes, the GPS signal (coming from outside the atmosphere is slowed briefly by a predictable amount. If this deceleration is accounted for in the receiver, the timing skew can be subtracted, and greater accuracy is achieved. Further reading: GPS Satellite Surveying by Alfred Leick (John Wiley & Sons, 1990) or Guide to GPS Positioning by David Wells et al. "Poor Man's Cruise" front page,Wall Street Journal, August 26, 1993 GPS World Magazine GPS Report (pricey) P.O. Box 10460 7811 Montrose Road Eugene, OR 97440 Potomac MD 20854 503-343-1200 301-340-2100 and an excellent primer on GPS "the new utility" from Trimble: Trimble Navigation 645 North Mary Ave Sunnyvale CA 94086 408-481-2994 art_lange@trimble.com ______________________________________________________________________ Q5.3: What can you tell me about map projections? From: John Ganter <jganter@sandia.gov> Map Projection Bibliography: http://thoth.sbs.ohio-state.edu/snyderbib/ The "bible" of map projections is often considered to be: Snyder, J. P. 1987, Map projections--a working manual: U.S. Geological Survey Prof. Paper 1395, 383 p. Reprinted 1989 and 1994 with corrections. [General work superseding Snyder, 1982, Map projections used by the U.S. Geological Survey: U.S. Geological Survey Bull. 1532.] Available for $32 + 3.50 S/H from: USGS Information Services, Box 25286, Building 810, Denver Federal Center, Denver, CO 80225, 303-202-4700; Fax 303-202-4693. ______________________________________________________________________ Q6.1: What are e-mail and paper addresses, and WWW sites of some vendors? For a complete USMail address list of GIS and mapping vendors, consult the GIS Sourcebook (annual) from GIS World Magazine. ------- Caliper Corporation Product: GISP+, Maptitude 1172 Beacon Street TransCad, GISDK Newton, MA 02161 (617) 527-4700 (617) 527-5113 (Fax) info@caliper.com (product information) support@caliper.com (technical support) http://www.caliper.com/ ------- Coherent Research, Inc. (CRi) One Adler Drive East Syracuse, NY 13057 Voice: 315/433-1010 Fax: 315/433-0070 Email: info@cri.com ------- Election Data Services, Inc 1225 I St NW, Suite 700 Washington DC 20005 202 789-2004 FAX 789-2007 The place to call for just about anything related to USA election data. ------- EROS Data Center Mundt Federal Building Sioux Falls, SD 57198 Fax: 605-594-6589 Customer Services: 605-594-6151 ------- Environmental Systems Research Institute (ESRI) 380 New York Street, Redlands, CA USA 92373 (714) 793-2853 support@esri.com http://www.esri.com/ For Help with ESRI products, you can send email to the above address. In correspondence be sure to include your name, organization, system, OS revision, Arc/Info revision and your ESRI client number (if you know it). ------- Etak The e-mail address for more info on the Etak road map and vehicle navigation software is ramaa@etak.com. ------- Genasys http://www.genasys.co/ "genasys-l" the mail list for users of Genasys related GIS. Subscription requests made to: majordomo@genasys.com Body of message to include... subscribe genasys-l your_login@host.domain (Your Name) ------- Generation 5 Technology, Inc. Products: Geo/SQL, Sheridan Park 8 8670 Wolff Court Suite 200 Westminster, Colorado 80030 Phone: (303) 427-0055 ------- Geographic Data Technology, Inc. (GDT) 11 Lafayette St Lebanon NH 03766 800-331-7881 (sales/voice mail) 603-643-0330 FAX 643-6808 Internet: don_cooke@lyme.gdt1.com ------- IBB Bahnhofstr. 43 40764 Langenfeld Germany Tel.: +49 2173 9153 10 Fax.: +49 2173 9153 30 GTI/RDB (geographic technical informationsystem/relational database) ------- InFoCAD Digital Matrix Services, Inc. 3191 Coral Way, #900 Miami, FL 33145 Ph: (305) 445-6100 Fax: (305) 442-1823 BBS: (305) 529-9303 email: rwelebny@attmail.com ------- Ingres (Intelligent DataBase), An ASK Company (this may be of new interest here because of the ability to define data types in the database, such as polygon, line, etc ) 1080 Marina Village Parkway Alameda, CA 94501-1041 510-769-1400 or (NA only) 1-800-4-INGRES Ingres' email address: firstinitiallastname@ingres.com A volunteer address for referals: morsie@ingres.com ------- Intergraph Corporation Utilities & Mapping Sciences Division Huntsville, Alabama 35894-0001 Mail Stop: IW17B5 Internet: info@intergraph.com U.S. 800-345-4856 (toll free) Canada 800-461-5297 (toll free) Asia/Pacific 852-893-3621 Europe 31-2503-66333 Middle East 971-4-367555 All Other 205-730-2700 (U.S.) ------- IBM Corporation Dept 44GA/075 522 South Road Poughkeepsie, NY 12601-5400 phone: 800-325-2733 email: ibmgis@vnet.ibm.com Products: Graphics Program Generator (GPG) geoGPG/6000 geoManager geoManager/6000 ------- MapInfo Corporation One Global View Troy, NY 12180 Voice: 518-285-6000 Fax: 518-285-6060 Sales: 800-FAST-MAP sales@mapinfo.com Tech Support: 800-552-2511 techsupport@mapinfo.com http://www.mapinfo.com/ ------- SHL Systemhouse Inc. 50 O'Connor Street, Suite 501 Ottawa, Ontario Canada K1P 6L2 Tel:(613)236-1428 Fax:(613)567-7892 SHL Systemhouse's email address: firstinitiallastname@gis.shl.com I can be contacted at jlee@gis.shl.com. GeoVision Systems Limited 80 Park Street Camberley, Surrey GU15 3PT UK Tel: 0276-677707 (From North America 011-44-276-677707) Fax: 0276-676567 ------- SICAD (BS2000) and SICAD/open (Unix) For the USA: Siemens Nixdorf Information Systems Inc. 200 Wheeler Road Burlington MA 01803 Phone (617) 273 0480 Fax (617) 221 0231 Headquarters: Siemens Nixdorf Informationssysteme AG International Business Development Otto-Hahn-Ring 6 81730 Muenchen Germany http://www.sni.de/public/sicad/sicad_us/sicad.htm ------- Smallworld Systems Ltd. Brunswick House 61-69 Newmarket Road Cambridge England CB5 8EG Phone (UK): 0223-460199 Email: help-desk@smallworld.co.uk Grid ref (UK): TL 460 589 ------- Strategic Mapping Inc Products: Atlas GIS, Atlas Graphics ... 3135 Kifer Road Santa Clara, CA 95051 Telephone: (408) 970 9600 (408) 970 9977 (Product Support) Facsimile: (408) 970 9999 UK: 44-753-621199 Europe: 31-30-650-936 e-mail: 71333.2457@compuserve.com ------- SYSTEM 9 can be reached at the following address: Arthur Berrill Arthur@system9.unisys.com Unisys 61 Middlefield Road Scarborough, Ontario M1S5A9 Canada (416) 297-2500 ------- TYDAC Technologies Inc. Product: SPANS 2 Gurdwara Road Suite 210 Nepean, Ontario Canada K2E 1A2 tel: (613) 226-5525 fax: (613) 226-3819 For questions, queries or quandries in regards to our product please contact wcsintda@ccs.carleton.ca _____________________________________________________________________ Q6.2: What public domain or shareware GIS/carto software is available and where is it? This list seems to be growing with software that does indeed have a price, so the wording of the question may be misleading. ------- See also: http://www.boco.co.gov/gis/gissoftware.html http://www.avenza.com/link2trans.html Atlas GIS You can buy it for $60 from the AAG Microcomputer Specialty Group. Send all Atlas GIS for DOS orders to Eugene Turner, Dept of Geography, California State U, Northbridge CA 91330 E-Mail: eturner@huey.csun.edu Purchase orders acceptable, but checks perferred. ------- General Cartographic Transformation Package or GCTP This is a package of FORTRAN procedures that provides forward and inverse projection of about 23 cartrographic projections. It is the "official" system of the National Mapping Division (NMD) of the US Geological Survey. It also provides conversion of State Plane Coordinate System. It is documented with *.txt, *.ps and word processor files as well as hard copy manuals. It is currently available via ftp from: nmdpow9.er.usgs.gov (130.11.52.92) as file public/amdahl/gctpv2.dat It is also available from: Phone: 1-800-USA-MAPS Fax:: (703) 648-5548 At the moment, prices for mail-order material is unknown. For software questions and assistance contact: Mike Linck Phone: (703) 648-4667 Fax: (703) 648-4722 E-mail: mlinck@usgs.gov U.S. Geological Survey 510 National Center Reston, VA 22092 The General Cartographic Transformation Package (GCTP) was converted to the C programming language, and several new projections were added. This new version, GCTPc, is being made available informally by EDC. The directories and files containing this package are available via anonymous ftp. Periodic updates and corrections will be put in this directory for access by the science community. Descriptions of these updates will be added to the README file in the main directory. The Package has been tar'd and compressed under the directory name gctpc. To access GCTPc, retrieve the file gctpc.tar.Z by anonymous ftp from edcftp.cr.usgs.gov This file can be retrieved by following these steps: ftp> cd pub/software/gctpc ftp> bin ftp> get gctpc.tar.Z ftp> quit Then on a UNIX system type: % uncompress gctpc.tar % tar -xvf gctpc.tar ------- The National Geodetic Survey (NOAA/NGS) provides many FORTRAN procedures and DOS programs for cartographic projections as well as datum conversions and other geodetic information. At this moment, the only way to get this material is by phone or mail ordering although there appears to be some effort afoot to establish Internet access. Contact (they take plastic): NOAA, National Geodetic Survey, N/CG174 1315 East-West Highway, Station 9202 Silver Spring, MD 20910-3282 Phone: (301)713-3242; FAX (301)713-4172 Mon-Fri 7 a.m.-4:30 p.m. Eastern Time. For complete list of products, ask for "Catalog of Products and Services of the National Geodetic Survey" and "Geodetic and Charting Publications". Prices are nominal for most software products (~$30 US) and *certainly* better than the $90+ they were charging in 1992. ------- GIV Geologic Information Visualizatio mapping software This PC based software from the USGS allows a user to turn a paper map into digital data, display and manipulate different image types, combine maps with images and text, and integrate data. Contact Christine Cook, USGS at 703-648-6481 (email ccook@usgs.gov) for information. ------- GeoSim, developed at Virgia Tech depts of Geography and Computer Science Project GeoSim consists of a series of self contained modules that serve as lab excersizes compatible with intruductory geography courses. These modules are appropriate for students at both the undergraduate and high school level. Educational goals are based on the widely adopted 'Guidelines for Geographic Education' (1994) co-authored by GeoSim team member Robert W. Morrill. GeoSim modules are interactive, allowing students to make decisions and manipulate geographic data in ways that encourage learning while maintaining student interest. The software runs on PCs, Macintoshes, and machines running X-windows. The modules include: Migration Modeling of the US, Migration and Sense of Place, Migration and Political Power in the US, Human Population, and Maps and Mapping. The software is available vi ftp and gopher at geosim.cs.vt.edu or via the WWW at http://geosim.cs.vt.edu ------- IVMAPS ivmaps, a package of map display software for USGS and DMA digital map data, is now available. It can be retrieved via e-mail by sending "get ivmaps ivmaps-0.4.1.tar.gz" as the body of a message (no subject required) to listproc@viewport.com, or ftp'ed from ftp.netcom.com (/pub/jg/jgautier/ivmaps-0.4.1.tar.gz). ivmaps is a collection of C++ class libraries and example display programs that support both DLG and VPF map formats in a common framework. Built on PROJ-4.3, ivtools-0.4, InterViews 3.1, and Unidraw, the software represents a reasonable starting point for the construction of custom interactive map-based user interfaces. Currently supported databases include DCW and DLG 1:2M. ivmaps has been built and tested on the following Unix/X11 platforms: SunOS 4.1.3 (MIT's X11R5, gcc-2.5.8) Irix 5.2 (SGI's X11R5, gcc-2.6.1) Linux 1.2 (Slackware 2.2, XFree86 3.1, gcc-2.5.8 and gcc-2.6.4-elf) It should be fairly straightforward to build on other Unix platforms with gcc, and perhaps with other compilers as well. Please send us diffs and build instructions for other platforms if you are able to build it. ------- megatelVISOR 1.51 - Hybrid vector/raster map server for user-written client applications - megatelVISOR enables the user to perform complex manipulations of text and graphics data against a map background. The core of megatelVISOR is a so-called "VIEWER" which allows to record, store and recall maps (drawings, pictures, charts, etc. ) of any magnitude. The magnitude of the scanned maps is only limited by mass-storage capability restrictions. Raster mapping The map-data input, i.e. the scanning of the graphic mass data (maps, plans, aerial reconnaissance photos, etc.), can be done by a standard scanner . The data are then compressed and stored on hard disk or CD. The handling of the scanning process and the storage is very simple, so that non-technical users may scan the maps without difficulties. The stored maps can be accessed from MS-DOS and UNIX UNIX users of megatelVISOR via network. megatelVISOR via network. Vector mapping megatelVISOR supplies diverse functions for graphic vector editing on the map (drawing, moving, copy/paste, colouring, hatching etc) that are provided by standard graphics systems running under MS-WINDOWS 3.1, NeXTSTEP, OpenStep and X-WINDOWS, Windows NT. The input for the generation of the vector layers is possible from the workstations manual I/O facilities (keyboard and mouse) as well as the import of vector data from ASCII delimited format (DXF and others). The vector-management system of megatelVISOR 1.5 consists of a new geometrical-database, based on a reorganisation-free v-tree-index procedure that provides a very fast access even when there is a very high number of vector objects to handle. Features of the resulting map (basic rastered map plus vector layers) are configurable from menue, which is adapted and similar to that of the graphical user interface GUI (e.g. MS-WINDOWS, NeXTSTEP, MOTIF ) so that non-technical users can perform all editing functions. megatelVISOR is a universal front-end for graphical applications. The VIEWER exchanges messages with other applications via DDE (MS-WINDOWS VIEWER) TCP/IP and Distributed Objects (UNIX Viewers). This includes external control of viewing functions, drawing by other applications as well as editing these (or new) objects in the VIEWER and sending them to the appropriate application. The incorporation of data files compatible with ASCII delimited format is possible. By (Mouse-Click-) adressing a layers graphical information (i.e. point,polygon or area) the target information of the database (or the text processor) will be searched and displayed with all stored attributes. Reversely the results of database manipulations may be displayed on the layer/map. Possible applications include technical documentation and land management systems. Prices (1Q1996) DM 7800.00 plus VAT. The program package megatelVISOR consists of several parts. Item prices in Deutsche Mark (DM) are given without VAT: Number of licenses 1 2-9 10 and more Viewer 3950 3550 3250 Toolbox 3950 3550 3250 Additional DXF-Interface DM 230. You only need the toolbox if you want to generate maps from scans. Please address project specific questions to megatelVISOR-Team R. Gath, Dr. H. Bischoff email: info@megatel.de megatel GmbH Wiener Strasse 3, D-28359 Bremen, Germany Tel. ++49 421 22095-0 , Fax ++ 49 421 22095-16 ------- GMT GMT (generic mapping tool) by Paul Wessel, School of Ocean and Earth Sciences and Technology (SOEST) / University of Hawaii can - display various kinds of fancy maps (Postscript from formatted ascii data) - apply diverse analyses (fits, contours, fft, etc) on the data - transform to many coordinate systems - run in connection with NetCDF - be used in connection with own routines more info can be got from reading the (thick) manual. GMT documentation & sources: anonymous ftp from kiawe.soest.hawaii.edu (128.171.151.16). in the pub/gmt directory GMT uses several functions in the netCDF library. Copy the file netcdf.tar.Z from unidata.ucar.edu (128.117.140.3) using anonymous ftp. Then uncompress/tar and follow their instructions for installation. ------- GRASS The U.S. Army Construction Engineering Research Laboratory's (USA-CERL) Geographic Resources Analysis Support System (GRASS) was developed to provide management tools to Army environmental planners and land managers. GRASS also has many applications for Civil Works project planning and design. GRASS has many capabilities, including the handling of different representations of data: RASTER DATA -- raster (or grid cell type) data can be used for analyzing, overlaying, and modeling areal features such as soil types or forested areas. VECTOR DATA -- vector data can be used to represent linear features such as roads, streams or area edges and can be combined with raster data for display purposes or for analysis. POINT DATA -- point data can be used to represent landmarks or the location of significant sites. From: wade@zorro.cecer.army.mil (Scott Wade) One way to obtain GRASS is via anonymous ftp from moon.cecer.army.mil [129.229.20.254]. It is available at any time. This is complete message form Office of GRASS Integration: From: Ken Brownfield <brownfld@max.cecer.army.mil> The OGI GRASS FTP server has been moved and reorganized. The FTP site is now available 24 hours a day, seven days a week. (!) The name of the new FTP site machine is still moon.cecer.army.mil, but the IP number has changed to 129.229.20.254. From any Internet machine, moon.cecer.army.mil should still work fine. After connecting to the moon, change your directory (using cd) to the grass directory. Since the new site is shared between many offices here at cerl, grass is in its own directory on the ftp site. The site has been reorganized in a more intuitive manner, so programs and updates should be easier to find. When GRASS v4.1 has been released, bug fixes will be separated from new programs and existing program _upgrades_. We hope that the lifted time limitations will give everyone a chance to access the FTP site at normal working hours. If you have problems, comments, or suggestions, please send mail to ftp- admin@moon.cecer.army.mil. ---------- MOSS MOSS for the IBM PC can be found on ftp.csn.org [128.138.213.21] in the /COGS/MOSS directory. PC MOSS contact: Sol Katz skatz@dsc.blm.gov FTP contact: Bill Thoen <bthoen@csn.org> I have recently posted the source code to PC MOSS at ftp.csn.org. To get it, ftp to ftp.csn.org and look in the COGS/MOSS directory for mosssrc.zip and mosssrc2.zip. It's public domain code and written in FORTRAN. MOSS is a vector-based GIS system widely used by the US BLM and others. The workstation version is several revs ahead of the PC version, and (in case you're wondering) the PC version is no longer being updated. The MOSS source code (and many other GIS-oriented files not on this ftp site) can also be found on GISnet BBS. GISnet's number is (303) 447-0927, (Boulder, Colorado) and you can call anytime at 1200, 2400, 9600 baud. However file downloading from GISnet requires a subscription ($48/yr), but you *can* download the full list of files, and a few other files for no charge. Please don't ask me questions about how to compile, link, etc. or anything about the algorithms involved in this code. I just put this out there because I think it may be of interest, but I can't offer tech support, because I don't know it very well myself, and besides, the code is fully self-documenting anyway... (muhaha!) The source code for PC MOSS as well as the executables (and manual) are on ftp.csn.org (128.138.313.21) in the /COGS/MOSS directory. The pc code is several rev's behind the current version. Current version is available from the blm in prime magsav format for about $250. or in ascii for about $500. (cost of distribution). also autometric inc. distributes an UNIX X-windows version, contact them at 303-989-6399 (fax 303-989-5799) Although MOSS is PD, to my knowledge, no one who has acquired it has posted it on a FTP site. The vector portions of the current version have been ported to 3 different operating systems. It is believed that a port to the PC would not be difficult. For those brave souls who might be considering porting PD MOSS to a new platform, a copy of the moss programmers manual has been uploaded to dsc.blm.gov in the ftp/pub/gis directory. ---------- Arcview 1.0 for Window 3.x Available via ftp at http://www.esri.com/ ---------- Arc Digitised Raster Graphics (ARDG) From: schuster@seas.gwu.edu (John Schuster) Code for viewing ADRG (Arc Digitised Raster Graphics) files is available on the GRIPS II CD-ROM. The U.S. Army Engineer Topographic Labs (Juan Perez) gave me permission to post the code on the net, so I've posted adrg.zip to spectrum.xerox.com. The GRIPS II (Gov. Raster Image Processing Software) CD-ROM is available from CD-ROM Inc. at 1-800-821-5245 for $49. Special thanks to Peter Z. Simpson for pointing this out. ---------- OzGIS Mapping System Version 10.3 OzGIS is a software system for displaying geographically referenced data, such as Census data or environment data, as maps and diagrams on screens, printers and plotters on an IBM PC compatible. DOS and WINDOWS versions are available. The OzGIS mapping system is available for anonymous ftp from many sites. Both DOS and WINDOWS versions are available from the SIMTEL20 archive and mirrors: OAK.Oakland.Edu (141.210.10.117), wuarchive.wustl.edu (128.252.135.4), archive.orst.edu (128.193.2.13), ftp.uu.net (137.39.1.9), nic.funet.fi (128.214.6.100), src.doc.ic.ac.uk (146.169.3.7), nic.switch.ch (130.59.1.40), archie.au (139.130.4.6), or nctuccca.edu.tw (140.111.3.21). The WINDOWS version is available on the major FTP site ftp.cica.indiana.edu and mirrors in directory pub/pc/win3/misc: 530-USA Sites: wuarchive.wustl.edu [128.252.135.4] 530- gatekeeper.dec.com [16.1.0.2] 530-Non-USA Sites: monu6.cc.monash.edu.au [130.194.1.106] (Australia) 530- nic.funet.fi [128.214.6.100] (Finland) 530- ftp.uni-stuttgart.de [129.69.8.13] 530- ftp.iij.ad.jp [192.244.176.50] (Tokyo) 530- ftp.technion.ac.il [132.68.1.10] (Israel) 530- src.doc.ic.ac.uk [146.169.2.1] (London) The DOS software is available as 7 files OZD101A.ZIP to OZD101G.ZIP, and the WINDOWS version as 13 files OZW103A.ZIP to OZW103M.ZIP You should also get a copy of Info-ZIP's free portable UNZIP program, which is recommended for these archives. It is file unz50p1.exe in directory /pub/msdos/zip This is a self extracting file i.e. just type UNZ50P1 and you end up with UNZIP.EXE which you use as e.g. "UNZIP OZD103A" to unpack each of the files. You should look at the file OZ*A.ZIP first as it contains a set of example maps and basic specifications as text files. You need to put the file in a new \OZGIS on your PC hard disk,UNZIP it, and type OZDEMO. The demo displays a series of saved screens (standard VGA) that should give a good idea of the capabilities of OzGIS. Requirements: DOS6.0: 286, 640K ram, EGA, 8meg disk WINDOWS3.1: 386+, 4meg ram, mouse, 8meg disk The basic price of OzGIS (until end 94) is A$500 (US$350), with educational discounts and various options. VISA and Mastercard accepted. See the ORDER.DOC file. OzGIS is developed by The Clever Company, QMDD box 6108, Queanbeyan, Australia 2620. ---------- The Defense Mapping Agency (DMA) is also a source of considerable cartographic software and information. Unlike the NMD/USGS and NGS, DMA information is international in scope. Some products (mostly maps) are sold through the USGS, but an outlet for software and other geodetic information is currently unknown. ---------- Fractal Landscape Generators Many people have written fractal landscape generators. For example for the Mac some of these generators were written by pdbourke@ccu1.aukuni.ac.nz (Paul D. Bourke). Many of the programs are available from the FTP sites and mail archive servers. Check with Archie (a well known example is Fractint - besides fractal images, it generates height fields). ---------- U.T.M. and State Plane Coordinate Conversion Software This program by John Banta is Windows shareware and is available at http://www.connect.net/jbanta ---------- R2V R2V for Windows and Windows NT, a raster to vector conversion system. The system combines the power of automatic digitizing technology with a menu-driven graphical user interface in the Microsoft Windows and 32-bit Windows NT environment. System features: Input: Images in TIFF format, supports bi-level, gray scale and color images. No software limit for image sizes.Also supports SPOT satellite image format. Output: MapInfo(MIF), DXF, ArcView 2 and Arc/Info vector file formats and TIFF format for images. Vectorization: Fully automatic and fast. It extracts vector data from maps, aerial photos and even satellite images of bi-level, gray scale or color types. Vector Editing: A complete vector editor is provided using the scanned image as backdrop. Image Processing: Vertical and horizontal flip, transpose, crop a region, smoothing using median filter, negate. Pixel values can be viewed in realtime using the Pixel Tool. Various image type conversion functions. Vector Registration and Merge: Registration is performed using a geometric transformation derived from user specified control points. Multiple vector sets can be merged into a single set. Print: Any printer supported by Windows. Demo: A demo version of the system is available by anonymous ftp at ftp://ftp.std.com/pub/r2v/r2vdemo.zip or disk by request. Prices: US$1495.00 US$960.00 for educational use. For more information, please contact: Able Software Co., 5 Appletree Lane, Lexington, MA 02173 Phone: 617-862-2804 FAX: 617-862-2640 Email: able@world.std.com _____________________________________________________________________ Q6.3: Will GRASS run under LINUX OS on my PC? From Mark Line <markline@henson.cc.wwu.edu> For GRASS 4.1 I've found these binaries to be plug-and-play. They're the newest version of GRASS. You can mention me (Mark) as a source of information on GRASS on Linux, if you want. _____________________________________________________________________ Q6.4: How do you convert ARC coverages to IDRISI? From: Mike Killion <mike@geogsun.geo.ukans.edu> To convert an ARC/INFO coverage to an IDRISI image (.img) file - 1) use the ARC command POLYGRID to convert the ARC coverage to an ERDAS 16-bit file (there are other options,but this one has been the least trouble in my experience.) You will need to provide the coordinates of the lower left corner of your coverage,and information about cell size(cell resolution, number of rows and columns), and you'll need to specify one numeric item to be used as the "z-value" for the new raster image. 2)use the IDRISI command ERDIDRIS (locate under the Import/Export menu) to convert the ERDAS file to an IDRISI image file. Before the new IDRISI image can be used, you'll have to create a documentation file for it. Another option is to UNGEN your ARC coverage then use the 3DRISI command 3RCIDRIS, but I've never had much luck with this one. ----- _____________________________________________________________________ Q6.5: How do I convert ARC coverages to GRASS? [Ed. note: As with most lists, this one has been edited due to length.] For help with ESRI products and importing or exporting data formats, see the ESRI web site http://www.esri.com From: Steve Bower <steveb@VCGI.UVM.EDU> SUMMARY: Arc/Info -> GRASS data conversions. ---------------- From: cg@cast.uark.edu TOPIC: Convert a polygon coverage from Arc/Info to GRASS Use a coverage named 'school' as an example to show the procedure: STEP 1. --- Get data out of Arc/Info 1.1 get line data Arc: ungenerate line school school.lin 1.2 get label point data Arc: ungenerate point school school.lab 1.3 get label text (attribute) data from INFO ENTER COMMAND >OUTPUT ../school.txt ENTER COMMAND >SELECT SCHOOL.PAT 12 RECORD(S) SELECTED ENTER COMMAND >LIST PRINT (See Note2) ENTER COMMAND >Q STOP school.txt should look like this: $RECNO AREA PERIMETER SCHOOL# SCHOOL-ID SCHOOL-NAME 1 -2.46815E+09 216,729.700 1 0 2 3.871248E+08 121,106.100 2 5 Springdale 3 2.923594E+08 114,518.100 3 11 Fayetteville 4 2.754085E+08 144,500.300 4 6 Prairie Grove (See Note1) 5 83192210.000 54,980.120 5 7 Farmington 6 98547120.000 53,769.720 6 4 Siloam Springs 7 3.852254E+08 112,999.100 7 3 Lincoln 8 2.611844E+08 101,406.700 8 1 Elkins 9 1.898218E+08 112,633.000 9 8 Greenland 10 2.734009E+08 101,322.400 10 9 West Fork 11 1.676338E+08 66,904.990 11 2 Winslow 12 54256160.000 32,175.590 12 10 West Fork STEP 2. --- Bring data into GRASS 2.1 create a subdirectory called 'arc' in your current mapset if necessary and copy school.lin school.lab school.txt to the 'arc' directory GRASS 4.1beta>v.in.arc type=polygon lines_in=school.lin points_in=school.lab text_in=school.txt vector_out=sch_dist idcol=5 catcol=5 attcol=6 GRASS 4.1beta > v.support map=sch_dist Note1: If the attribute text contains blank,(for example,Prairie Grove), the second word is dropped after running 'v.in.arc'. My only suggestion is to edit the dig_cats file so that the complete attributes can be retained. Note2: If the PAT file contains a lot of columns, you have to use the INFO command - REPORT to create a report which looks like the above example(school.txt). For more information about REPORT refer to INFO Reference Manual. ---------------- 1) UNGENERATE the ARC coverage. Coverages that will end up as GRASS vector files need only lines, e.g. UNGENERATE lines <your_coverage>. Those that contain polygons and are destined to become raster layers need lines and points, eg: UNGENERATE lines <your_coverage> <lines_output_filename> UNGENERATE points <your_coverage> <points_output_filename> Next, use DISPLAY or PRINT (I think-- this is from memory) from within INFO to print out the fields you need from the database. 2) Move all of the ungenerated files and the database text files to $LOCATION/arc-- you'll probably have to create the arc directory yourself. The files MUST be in this directory. $LOCATION is defined by GRASS at startup, so if you mv them from within a GRASS session, they'll go to the right place. 3) Use v.in.arc to suck the files into GRASS. The g.manual entry explains things pretty well. This is probably where problems will occur if any occur at all. This program is touchy about the format of the ungenerated file. 4) Run v.support on the resulting file. Be sure to use the <build> option. In my experience, v.support generates tons of error messages, but few of these are ever significant, so don't let them throw you. 5) Run v.digit on the v.support output. At a minimum, run v.digit with no digitizer (mouse mode), fill in the information regarding scale, window boundaries, etc, then let v.digit draw the file. When it finishes, you can either save the resulting vector layer as is or modify it. If it is destined for raster-hood, you should probably check and make sure that all polygons are closed-- see the v.digit tutorial for additional details if you need them. 6) If you want to build raster coverages, run v.to.rast on the vector layer after v.digit. As I recall, v.to.rast creates a HUGE temporary file, so be sure you have lots of disk space available. 7) Run r.support to assign a color table, check category labels, etc. Voila-- you're done! Michael Camann camann@dial.pick.uga.edu ______________________________________________________________________ Q6.6: Where can I find some AMLs to look at? AMLs and other ESRI scripts are available at http://www.esri.com/scripts/scripts.html Also: ftp://wigeo.wu-wien.ac.at/pub/acdgis-l/aml For information on ESRI Inter-Application Communication, with AML, Avenue, and Visual Basic code samples, see: http://www.sandia.gov/GIS/tutrs/iactut2.html And there is the following book: ESRI part number 420259 ARC Macro Language: Developing ARC/INFO menus and macros with AML. The unit price is $50.00 (U.S.) and discounts are available as follows: 10% for university faculty & students (copy of valid photo-ID required) 10% discount for federal government 40% discount for educational institutions and bookstores Shipping: $10 for surface; $15 for second-day air; $26 for overnight UPS. Sales tax: payable in many states Form of payment: check, purchase order, or Master Card/Visa Order from: Attn: Customer Support Workstation ESRI 380 New York Street Redlands, CA 92373 Fax: (909) 793-4801 Telephone: (909) 793-2853, ex. 2050 (credit card orders only) THE ABOVE IS DOMESTIC U.S. ONLY! INTERNATIONAL ORDERS MUST BE PLACED THROUGH THE LOCAL ARC/INFO DISTRIBUTOR. ______________________________________________________________________ Q6.7: How can I convert ARC files to some other graphics formats? Summary From: Fred J. Calef III <mapduxbury@UMBSKY.CC.UMB.EDU> POSTSCRIPT: It seems the postscript file Arc/INFO makes is not a true Encapsulated Postscript File. It seems to be a little more than a plain postscript file but not quite an EPS file. Here are some solutions. 1) Use the unix2dos command on unix systems to add control-returns to the file which dos needs to read the file properly (Arc/INFO's postscript file being an ASCII file) 2) FTP the file using the ASCII option because the postscript file is in ASCII format 3) Use the Ghost Script utility (available via FTP) to read the file, then output it in EPS format. ****As a special note, GhostScript can be FTPed from prep.ai.mit.edu in directory /pub/gnu. 4) Use a program that reads pure ASCII postscript files (such as Word on the Macintosh) ADOBE ILLUSTRATOR: This file format is similiar to postscript, but with some differences (whatever they are). I received some specific responses to correcting this format. 1) Edit the file and add these lines after the line containing %%EndProlog (said to be line 8): %%BeginSetup %%EndSetup This supposedly makes it readable with Corel Draw. 2) Make sure you close the file by issuing another DISPLAY command or QUITting out of Arcplot. This puts the bounding box around the file. 3) You can run an awk program in the unix environment to fix the file. Here is the command line: nawk -f fix_ai.awk bad_ai_file > good_ai_file Here is the awk program: # Program to convert Arc/Info Illustrator output so Corel Draw # can handle it. { print; } /EndProlog/ { print "%%BeginSetup" print "%%EndSetup" } This should allow you to read the file in Corel Draw. TIFF: I have found one way to succesfully bring a TIFF file into the pc DOS environment. 1) FTP the TIFF file using the binary option. Then use Corel Draw (I used v3.0) to read the file with the PhotoPaint module. This successfully reads the file,but all of the areas using black are valued as white! On the screen there should be a pallette tool displaying all of the colors used in the image. Double click on the white block on the palette to bring up another tool that allows you to adjust the color to any in the spectrum. Move the red, green, and blue sliders to the opposite end of the slider spectrum. You can then press the preview button to see if this gives you the correct color scheme of the image. Then you can press the OK button to transform the image to the setting you changed it to. You should have the proper color balance now. Save the image to keep this change. (I've tried other programs to read the original Arc/INFO TIFF file, but came up with a black screen) Computer Graphics Metafile (CGM): The only response I received about this format was that they could not successfully use the Arc/INFO generated file. OTHER WAYS TO CAPTURE IMAGES IN ARC/INFO:Here are some other ways to capture images in Arc/INFO. 1) IN the UNIX environment, use the SNAPSHOT Utility (available via FTP) to capture the image off of the screen, then use HIJACK to convert it into another file format. The resolution is not suppose to be that great. 2) Import your coverages into ARCVIEW, make the image to be captured and use it to make a WINDOWS BITMAP image. 3) Output to an HPGL file, then use the Wordperfect utility GRAPHCONV.EXE to convert it to a .wpg file. Review the options of this utility (This solution came from a recent summary on putting postscript files into Wordperfect). These are the suggestions, but I have not personally verified them (except the TIFF suggestion which is my own).There has been alot of talk about these problems and I hope these possible solutions work out. Maybe ESRI can or has addressed these problems in 7.0...one can only hope... ______________________________________________________________________ Q6.8: How do Arc/Info and Intergraph MGE compare? Summary from: Chris Wade <cwade@gears.efn.org> *********************************************************** From: E7G4KIN@TOE.TOWSON.EDU At my company, data Chromatics, Inc. we use both arc/info and intergrpah mge. We perform a variety of GIS consulting services to public and private sector clients, with particular emphasis on data integration. For larger scale implementations, we prefer intergraph for two main reasons: 1. It is based on on industry standard cad package (Microstation) which is known by most people with cad or mapping experience and 2. The MGE database structure permits full use of standard SQL databases such Oracle, Informix or Ingres. In Arc, while you can use an oracle database, you can't use an oracle table...you must use the info table. Arc is not a CAD package. Since most large scale projects require traditional input work, your costs can be reduced by selecting a package with a direct (not translated) cad input function such as autocad or microstation. From the database standpoint, I can hire a database programmer in Oracle and, with little or no additional training, have him or her peforming query development for end users that may not need graphic interfaces. This is not easily accomplished with arc. On the smaller scale, Arc can be implemented with less training costs. *********************************************************** From: david@sparc.ecology.uga.edu There are some good programs from Intergraph that a GIS operation could probably be happy using. Raster to vector conversion software comes to mind. The basic product on which all Intergraph is based (Microstation - a CAD program) is quite good. However I found the following things about Intergraph to be quite irritating: 1. Since it was built on top of a CAD system, it is essentially a "kludge" system in my opinion. "Kludge" systems are inherently buggy I think. I would say that ArcCad probably suffers from the same kinds of problems (although I must admit I have never actually worked with it before). 2. If you are talking about Unix workstation platforms, then Intergraphs program only run on Intergraph equipment as far as I know. The I equipment seems to have a lot of hardware problems. Also the operating system is based on System 5 unix, and seems pretty primitive after working with BSD unix on Suns (this is probably another bias, and of course, Sun is moving to Solaris, which is also System 5 based - bummer!). 3. The software is menu based for the most part, which is probably good for most users. I however have a problem with "black boxes". I personally like command line software, because I feel I have a better understanding of exactly what I am doing. It is harder to learn of course. Even though Intergraph is menu based, there seems to be a excessive amount of system files that have to be dealt with by hand. I don't understand why the software does not take care of many of these files for the user. The idea of a menu interface is supposed to protect the user from this kind of problem 4. Packaging is a REAL problem I think. With Intergraph you have to buy a whole bunch of individual packages to put together a usable system. Most of the programs have descriptive names such as IPSNUC27, which is very informative to they purchaser (don't let the sarcasm drip on you). I don't think the sales people understand all the different pieces much less the prospective buyer. A/I (for the moment at least) comes more or less bundled. The basic package lets you do most of the GIS things you need to do. Add on's like COGO, are also bundles of programs. 5. Documentation is terrible, although it looks impressive on the bookshelf. 6. Creating your own menuing interface is a major problem with Intergraph. They use a programming language (MDL) which is very similar to C, but is not truly compiled. A/I's AML is much easier to develope with in my opinion. Of course, if you want to be sure you will be invaluable to your boss (assuming they commit to Intergraph), then do a lot of programming in MDL. This should guarantee job security because there are so few people who understand/want to program in this language. *********************************************************** From: HarleyP@MSMAIL.WAIRC.GOVT.NZ My impressions so far of Intergraph is that it is seems very hard to use (remember my A/I bias here). It is very different to A/I in its layout and how it requires you to do things but the end result will be the same. It has a wonderful windows interface and this helps immensely. It is much more stable than Arctools and heaps easier than command line entry and AML programming. However, for the dedicated types, there is a command line to do everything and you can customise Intergraph (though not as easily as A/I, but many wouldn't need to due to the friendly user interface which already exists). Intergraph can be run in batch mode so that many processes can be automated such as refreshing point coverages to take into account database changes that may have occurred during a days operations. Intergraph handles graphics better than A/I, that is because all graphics are controlled through Microstation CAD which is the core of the Intergraph GIS, as you probably already know. I feel that once I am used to Intergraph software I will be away laughing. All the functionality is there and then some ie Remote sensing and 3D add ons. I think that the dominant application that your GIS system will be put to is the most important thing to consider. If you are doing AM/FM, such as utilities management and lots of CAD type stuff than definitely go with Intergraph. Microstation is a wonderful CAD package and the GIS functionality is built on top of this. Intergraph has great 3D functionality and this appeals to us for its potential in monitoring air and groundwater pollution, flood hazard assessment etc etc. If your needs are more thematic and natural resource information based, then Arc/Info probably has the edge. *********************************************************** From: rcw@whitestar.com You probably have a short list of essential things you need to do - like build a parcel database. My brother Kip White, who works for El Paso County, CO, has just completed 1,500,000 parcels out of 3,000,000 using his Arc/Info system 6.1.1. So it works ;-) Note that these parcels are not digitized, but entered from plats using COGO measurements. You should probably do it this way and use GPS too for best accuracy. Lots of hard work. He has a group of 5 working with him on an older VAX installation. I'd ask for references, descriptions, and/or demos from each company. I've found I get a warm and furry feeling talking to people who were in my shoes a year a year ago. AMLs are a nice way to automate tasks for a particular situation. I'm an Arc user too, but I think some of the CAD technology in Microstation, which is what I'm familiar with on the Intergraph side, is second-to-none. I like the way Intergraph is efficient vis-a-vis digitizing techniques and drawing file sizes. Speed of access is very good to. So get yourself both! Arc/Info imports the IGDS files ;-) *********************************************************** From: geasson@umr.edu Intergraph's approach is to develop generic application that are built on their basic software of Intergraph Graphic Design Software (IGDS). Applications such as Scan Data Capture, which was sold as a separate software package were primarily macros written to combine IGDS functions. Whereas ARC/INFO gives you the "tool box" to develop your own specific applications. If you have the staff to write and maintain you applications, I feel that ARC/INFO is the way to go. However, Intergraph's support (both hardware and software) were fantastic. You had only one number to call and get you problems taken care of. *********************************************************** From: sonny@tfssun.tamu.edu I use and teach both systems on a regular basis. Like you, I cut my teeth on ARC, but I have used MGE and other Intergraph products enough to be fairly comfortable (I've even switched from using Erdas for remote sensing to Intergraph's ISI). connecting to a database: MGE on Clix or NT -- incredibly simple because of RIS ARC -- takes some work editing graphics: MGE -- uses Microstation for graphic manipulation, very nice CADD product ARC -- arcedit and ADS are clumsy in comparison simplicity of use MGE -- more complex to learn than Arc, requires more "gis" knowledge ARC -- relatively easy to learn despite the number of giga-commands data capture: MGE/Intergraph -- incredible amount of stuff that interfaces directly to MGE, we have retired our digitizers and use their vectorization (GEOVEC) and character recognition (ISCR) software for data capture ARC -- ADS and ARCSCAN (Haven't used ARCSCAN) operating systems: MGE ---on Clix (System V unix) or NT (I love NT, this comes from an affirmed unix head who has Linux on a home computer). NT is a stable and reasonably fast operating system. Setting up the network is laughably simple as is connecting to databases. ARC --Runs great on Unix boxes (I'm most familiar with SUN OS) *********************************************************** It's difficult to compare performance, since the platforms are so different. MGE runs on WinNT or an Intergraph Clipper with UNIX. I tried out the proprietary Clipper box. Even on the Clipper, MGE is not very standard, it uses a proprietary graphics interface instead of XWindows. The ARC/Info package, on the other hand, runs on most popular UNIX platforms (I used a fast Sun SPARC10) and uses XWindows for graphics. It's almost impossible to compare the performance between these two very different platforms. Both seemed acceptable in performance. Both products are "loaded". I'm confident that either will be able to "get the job done", regardless of the requirements. 1A. MGE architecture: MGE is built around a CAD system. If the planned geo-system is CAD-intensive, then MGE has a distinct edge. ESRI provides the ARC/CAD product to compete in this arena, but MGE is a CAD at its core. The data is stored in layers or covers. The product has a built-in GUI, but it is not that easy to use (Now let's see, which of these 500 buttons do I need to press?). MGE does come with a bundled C-language interface, which I consider important. 1B. ARC/Info architecture: ARC is also stored as covers. It is much more concerned with "topographical-correctness" than MGE. For example, when I move MGE data to ARC, ARC will find and gripe about edges that don't match, polygons that don't close, centroids that are missing, etc.. MGE never finds anything wrong with cleaned ARC data. If the planned geo-system is to be used for cartographic or polygonal study, then ARC would be a better choice. ARC/Info is command-line driven. You can build your own GUI, using the bundled ARCTools package as your prototype or you can just use the ARCTools as is. Eventually though, (if you are the programmer) you're going to have to learn those zillion command names. ARC/Info does NOT come with a 'C' interface; you must use their own AML language. I consider this a minus. *********************************************************** From: Bryant Ralston <rami@ksu.ksu.edu> I have worked with both and it really begins with the data structure of both packages. MGE is built on top of a CAD data model while ARC/INFO's data structure was built from the ground up as a topoligcal data structure. Therefore, ARC/INFO really was designed as a GIS while MGE was a CAD-program (Microstation) with a GIS toolbox grafted onto it. As a result, MGE requires more 'hands-on' managing of the associated databases while ARC/INFO manages the database for you. I personally am a geographer and consider myself more of a GIS user than a CAD user although I started in CAD design with AutoCAD. Now ESRI has an ArcCAD package similiar in nature to MGE but built on top of AutoCAD. Beware though to introductory GIS users or former AutoCAD users ArcCAD can be very confusing. All in all, to compare ARC/INFO to MGE really depends on what you want out of your GIS system and the amount of data you have and the form you have it in now. If you are a traditional Microstation user and have lots of design files then MGE is probably for you but be careful when you want to use ARC coverages because the attribute linkages do not translate very well. With ARC/INFO rev 7.02, they are supposed to be able to export RIS linkages for use in MGE but I haven't tried it yet. ___________________________________________________________________________ End of FAQ FOOTNOTE: (C) 1994, 1995, 1996 Lisa Nyman. This document may be distributed freely provided this copyright notice is included. Permission is not granted for commercial use. The mention of product trade names in no way endorses these products or the companies which develop and distribute them. Also, this document represents collective knowledge of many people. The editors, any government, or business are not responsible for errors in the content. Your mileage may vary. Any prices mentioned are of course subject to change. -- Lisa W. Nyman <lnyman@census.gov> |Standard Disclaimer: |In Karate one| ------------------------------------ |I speak for me, not U.S.|does not make| Personal email: lnyman@mindspring.com|________________________|the first | GIS FAQ: http://www.census.gov/geo/www/faq-index.html |move. |