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.