Use digital elevation model (DEM) files or SDTS files converted to a DEM format to import points into a surface.
DEM files are used to store and transfer large-scale topographic relief information for use in GIS, earth sciences, resource management, land planning, surveying, and engineering projects. DEM files typically contain land XYZ information at a regular grid-spaced interval to represent ground relief.
You can add and remove DEM files, and view DEM information. To transform DEM coordinates so they match the coordinate system of the current drawing when the surface is built, specify a coordinate system for the DEM file.
DEM files are a valuable data source for many planning and engineering tasks that might not need the type of precision gained by doing a ground or aerial survey. DEM files can also, in some places, completely eliminate the need for specific surveys. Usually, the DEM data is not precise enough to use on small-scale studies, but is ideal for large-scale planning and analysis tasks.
Some examples of projects that can benefit from DEM information include hydrologic studies, corridor planning for highways and pipelines, land use planning and analysis, slope analysis, and large-scale project visualization.
DEM files are widely available on the Internet. For example, the United States Geological Survey (USGS) provides many DEM files at their web site.
Topics in this section
- About DEM File Data
DEM files typically contain land XYZ information at a regular grid-spaced interval to represent ground relief.
- Adding DEM Files to a Surface
Use the Prospector tree to add DEM file data to a surface and to work with a DEM file data. The DEM file data is combined with any other surface data that you define.
- Changing the Specified Coordinate System of a DEM File
Use the Prospector tree to specify or change a DEM file coordinate system. If the DEM file coordinate system is different from the current coordinate system of the drawing, you can specify a coordinate system for the DEM file. The coordinate system you specify for the DEM file should match the data defined in the DEM file itself.
- Importing DEM Extents
You can import the extents of a selected DEM file into the drawing as 2D polyline objects.
- To zoom or pan to DEM file data
Zoom or pan to DEM file data, and view information about its data including its coordinate system, projection, and datum.
- DEM Files and Memory Usage
Large TIN surfaces, such as those built from DEM files, can require a substantial amount of memory (RAM and virtual memory) and disk space to build and save the surface. TIN surfaces require about 100 bytes per point, whereas grid surfaces require about 16 bytes per point.