DEM files come in several formats. You can import either OS (Ordnance Survey) DGM, ESRI Arc Grid, or GeoTIFF files.
Tip: You can also import DGM files into an existing surface. For more information, see To Add DEM Files to a Surface.
Click Home tabCreate Ground Data panelSurfaces drop-downCreate Surface From DGMFind.
In the Grid Surface From DGM dialog box, browse to the location of the file.
Select the DGM (.dgm), GeoTIFF (.tif), ESRI ASCII Grid (.asc or .txt), or ESRI Binary Grid (.adf) file. The filename is displayed in the File Name field.