Use digital ground model (DGM) files or SDTS files converted to a DGM format to import points into a surface.
DGM 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. DGM files typically contain land XYZ information at a regular grid-spaced interval to represent ground relief.
You can add and remove DGM files, and view DGM information. To transform DGM coordinates so they match the coordinate system of the current drawing when the surface is built, specify a coordinate system for the DGM file.
DGM 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. DGM files can also, in some places, completely eliminate the need for specific surveys. Usually, the DGM 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 DGM information include hydrologic studies, corridor planning for highways and pipelines, land use planning and analysis, slope analysis, and large-scale project visualization.
DGM files are widely available on the Internet. For example, the United States Geological Survey (OS (Ordnance Survey)) provides many DGM files at their web site.