Map Viewer Frequently Asked Questions

See also: About the Map Viewer and Details.

Q.: What are some other map services on the web?
A.: MapQuest, Tiger Mapping Service, Etak Demos, Earth Viewer, U.S. Relief Maps, BADGER, Weather Maps
Q.: What are some commercial map products?
A.: DeLorme, AutoMap, Etak
Q.: What are some other lists of map related web sites?
A.: Yahoo, GIS/Cartography Starting Points, Geography of Cyberspace
Q.: The borders for eastern Europe, the former USSR, and several other countries are out of date and incorrect.
A.: Sorry. The world map data used for this server is from 1985-1990. Please do not select the "borders" feature if these inaccuracies are a problem for you.
Q.: It would be nice if you had a page of links to a nice map of every state.
A.: A page with links for United States Maps is now available, thanks to Christian Campbell (ccampbell@tng.net).
Q.: Are there instructions for using the Xerox map viewer in other projects?
A.: See Map Viewer Lessons (by CurriculumWeb)
Q.: Why is it slow?
A.: The map rendering server is a SPARCstation 2 in Palo Alto, California. With a good network connection it seems to take a minimum of 2-3 seconds to retrieve a document with embedded map image. Time goes into reading and filtering the map vector data, rendering the image, converting the image into GIF format, sending it over the network to the client browser, and finally displaying it in your web browser. Changing resolution, geographical location, or map features can cause additional database files to be accessed (thus additional delays). If it takes longer than 5-10 seconds, the cause is most likely a slow network connection between your browser and the server.
Q.: Where do I find out more about map rendering programs?
A.: ?
Q.: How do I download a map image using a text-only Web browser (or retrieve the image to a file using a graphical browser)?
A.: Depending on the client software you are using, the following may work: select the Map Viewer's "Retrieve Map Image Only" option. Some browsers will then allow you to store the image to a local file.
Q.: How did you get the map images into gif format? Did you scan?
A.: The map images are not scanned, they are generated on demand from vector map data using software developed at Xerox PARC. The conversion to GIF format uses software derived from the public domain "pbmplus" graphics package.
Q.: Is the map viewer software publically available or for sale?
A.: Sorry, not currently.
Q.: What are the data sets used?
A.: The world map data is from the CIA World Data Bank II. The higher resolution U.S. data is from the USGS 1:2,000,000-Scale Digital Line Graph (DLG) Data.
Q.: Are the images generated by the map viewer copyrighted?
A.: The map data is public domain (courtesy of the U.S. government).
Q.: How do I get a copy of the CIA World Data Bank II database?
A.: Apparently it is distributed by the National Technical Information Service (NTIS).
Q.: How do I get a copy of the USGS Data Line Graph CD-ROM?
A.: Questions regarding availability and ordering of US GeoData (all types of digital cartographic and geographic data produced and distributed by the U.S. Geological Survey) should be addressed to:
Q.: Is there a net-source for DLG data?
A.: ?
Q.: The map document generates custom HTML documents in reponse to user events. Is the functionality I want part of the custom HTTP server that you mention, or is this functionality available as part of a standard WEB server?
A.: It is part of the custom HTTP server. However standard Web servers can be enhanced by adding custom software (CGI scripts).
Q.: Do you know of any programs for displaying the Cartographic data, DLG and DEM files, in the MSDOS environment?
A.: No, although there is a simple demo program on the USGS CD-ROM. I tried it once and it was very slow.
Q.: How do I save the maps I generate in a postscript format?
A.: The map viewer does not generate PostScript, but the client or image viewer you use may be able to. Try using the "Save As" or "Print..." (to file) options of your WWW browser or external image viewer.
Q.: Do the maps have labels (i.e. names of towns, roads, etc.?) Are they topographic with elevations? What I got was a "skeleton" with only a few line features shown.
A.: The map data we have contains only line data such as coastlines, borders, rivers, roads. We do not currently have the data or software to add labels or topographic information to the maps.
Q.: I am curious how you maintain the information that when I consecutively click on the same x-y-coordinates in successive pictures, I get a further zoom-in (how to reconcile this with the fact that the protocol is stateless and the URL is the same each time).
A.: The URL is not the same each time. All the necessary state including the latitude, longitude and scale parameters are included in each URL.
Q.: How about adding some descriptive information about the various map projections used?
A.: The three available map projections were chosen for their ease of implementation in that all parallels are equally spaced.
Q.: Tie this to the geography server so people could type names?
A.: It has been done by Brandon Plewe. See his U.S. Gazetteer server. Also see the US Census Bureau's U.S. Gazetteer.
Q.: How do I specify dimensions for the output picture?
A.: Use the /iwd and /iht options (example).
Q.: Can I mark the long/lat specified in the URL with a symbol?
A.: Use the /mark option.
Q.: The Map Viewer doc should show you the exact search string you typed (or could have typed) to get there.
A.: It does with the Hide Map Image option.
Q.: Is there a legend available for the map colors?
A.: See World Map Legend and U.S.A. Map Legend.
Q.: I see grid lines that look like they're about on 1 degree spacing. Are they really at 1 deg intervals?
A.: It automatically choses a spacing of 15, 10, 5, 3, 2, or 1 degrees depending on the scale.
Q.: The horizontal grid lines (parallels) appear to be at whole degrees of latitude from the equator. But the vertical (meridian) grid lines are centered on the center of the map, and are not whole degrees of longitude from Greenwich.
A.: Unfortunately this is true. It is due to the simple way the coordinate system rotation was implemented. I am afraid I have no time available to fix this.
Other suggestions from users:

Please send questions or comments to webmaster@xerox.com.

7-Apr-97