Using File - Import - Surface with the Files of type filter set to DTED files allows us to import NIMA Digital Terrain Elevation Data (DTED) data. This is a NIMA military format for terrain elevation. DTED data occurs in three resolutions: DTED Level 0 data is published in 30 arc second resolution for free public download. Higher resolution DTED Level 1 and Level 2 are available to NIMA's special friends. Manifold reads them all.
DTED files are georegistered upon import.
Download some DTED data in Military Specification format from the NIMA geospatial engine data server at:
The data is packaged as a zip file, which will unzip into a dmed file, and dted and text folders. Within the dted folder will be located other folders containing the individual DTED data tiles, usually in files ending in a .dt* extension such as .dt0. Import the .dt* files to create surfaces.
To tile the various surfaces into one big surface, use Copy and Paste to paste them all into one surface
For example, if in NIMA's server we zoom into the San Francisco Bay area and download the DTED data, after many long minutes of waiting the NIMA server will give us a link to a zip file. We download the zip file, unzip it and find that within the dted folder there are two folders, w122 and w123. Within the w122 folder are four files, n37.avg, n37.dt0, n37.max and n37.min. Within the w123 folder are also four files, also called n37.avg, n37.dt0, n37.max and n37.min. If we import both of the n37.dt0 files (one from the w122 folder and one from the w123 folder), we will end up with two surfaces, one called n37 and the other one called n37 2 (Manifold's default naming scheme appends a "2" to distinguish it from the identically named component already in the project).
The two surfaces show adjacent regions of the San Francisco Bay region. We can copy the n37 2 surface and paste it into the n37 surface to create a single, seamless surface showing the topography of the San Francisco Bay region.