What New


Doc and FQA

Screen Shot

Documentation and FAQ:


A manual for g3DGMV is in the works.


Where can I find DEM and DLG maps?

The following sites have lists of DEM and DLG maps for various areas. After you uncompress the map, make sure to rename it with the appropriate extension (dem or dlg). Note: g3DGMV does not work with SDTS formats at this time, use the standard DEM and DLG maps.

This USGS site has a list of DEM and DLG maps for various areas http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/ndcdb.html

10-meter DEMs for Southwest Washington

New 10-meter DEMs January/February/May 1999

you can now access the map from the file selector within g3DGMV.

What is the purpose of the combo box above the text window?

The combo box shows the reference Ellipsoid use for calculating positions on the map. An Ellipsoid is a mathematical structures that define the shape of the earth and that are associated with different datum's. Datum's describe the model used to match a features to ground coordinates. The default Ellipsoid is the Clark 1880. This is associated with the NAD 27 Datum. If a position on the map doesn't look right, try the WGS 84 or one of the other Ellipsoid listed.

This USGS site has more on Ellipsoids and Datum's. http://www.usgs.gov/

How can I convert SDTS-formatted DEM data to the older DEM format used by g3DGMV?
The conversion program SDTS2DEM, originally written by Sol Katz of the U. S. Bureau of Land Management, converts the SDTS-formatted DEM data to the older DEM format. The program is provided in two forms, one for Win32 platforms, the other for OS/2 and DOS platforms. You can down load the program from this site: http://geopotential.com/codes/sdts2dem.zip

This USGS site has more on Ellipsoids and Datum's. http://www.usgs.gov/

When I load a DEM file (it seems to work, progress bar, status bar...) But I only get a black screen. I can use the tools to draw on the canevas but there is no map. What is wrong?
This is due to the localization transform of string into float. For example in France, they write 5,45 and not 5.45. The problem is that strtod uses this localization to transform string into float. When French settings are used 5.45 is understood as 5.
So 0.4565332E6 is understood as 0....

Just by launching LC_ALL=en g3DGMV should solve this issue.

Do you have any comments about this site? Please drop us a line at yostn2000@yahoo.com