Mapping 

Sources of Computerized Mapping Information 

I've recently run across some resources for viewing on-line topological and other mapping data. I spent quite

a bit of time digging through web pages, and thought I'd record some of what I've discovered. I am not an expert in this area! Follow the web links for additional details. The material here is presented to give you a head start, no more. The material presented here is just the tip of the iceberg. Check out the links for much more information.

Free Software 

The following programs were all developed for Windows 95/98. These are also pretty resource intensive, so be prepared with a fair amount of PC horsepower. These programs were developed for different applications, and serve different purposes. In all cases, the setup programs take several megabytes of disk space. Don't plan on downloading them unless you have a high-speed connection (or a lot of time).

Dlgv32 DLG Viewer 

Dlgv32DLG Viewer

This program allows you to view Digital Line Graph files available from the USGS. This is the best program to assemble data similar to the standard topological maps you may be familiar with. Data is organized in layers, each layer is downloaded as a separate file. Once the layers are loaded, it is easy to select any area to zoom in or print. Layers from adjacent areas can be added, and the program will combine the data into a larger view.

The standard data available is from 1:100000 maps. Contour lines show 100 foot elevation changes. This is lower resolution than the 20 foot elevation changes seen in the 1:24000 topographical maps generally available.

DEM3D 

DEM3D

This program allows you to view Digital Elevation Model files available from the USGS. Once loaded, you can rotate and zoom the view. Options allow different viewing modes.

Terra Base 2 

Terra Base 2

This is probably the most powerful of the programs described here. It also uses DEM files, but allows numerous ways to view the data. Contour line resolution is selectable (in meters), and there are advanced features such as creating flybys from the terrain data. This program is more an analysis tool than a viewer. Unfortunately, only elevation information is readily available. Other features such as roads and water features are not overlaid.

Data File Types 

Data files for the programs above can be downloaded from USGS sites.

DLG: Digital Line Graph

 

DEM: Digital Elevation Model

 

Links