PhotoSat and GIS Terms

These are some commonly used terms and FAQs.


Because many of our clients come from engineering industries, we do not use GIS and CAD terms.

GIS and CAD Terms

There are several terms that are widely used in Geographic Information Systems (GIS) and Computer Assist Design (CAD) systems. Some of these terms are:

  • DTM: Digital Terrain Models (DTM) are elevation grids of the bare ground. All of PhotoSat’s satellite surveying products are DTMs.
  • DSM: Digital Surface Models (DSM) are elevation grids of the full visible earth surface. PhotoSat’s satellite mapping products are DSMs.
  • DEM: Digital Elevation Models (DEM) are either the elevation of the full visible earth surface, the tops of trees and buildings or the elevation of the bare ground beneath the tree cover and buildings. Our technology has the capability to create DEMs, however we have made a conscious decision not to offer these products.

PhotoSat Terms

PhotoSat conducts both satellite surveying and satellite mapping. These are unique products with different applications.

  • Satellite Surveying: Our elevation surveys are produced from stereo satellite photo pairs. They are highly accurate. In GIS terms, our elevation surveys are DTMs.

For a list of deliverables, see PhotoSat’s Satellite Surveying Products and Options.

  • Satellite Mapping: Our mapping products are also produced from stereo satellite photo pairs. With mapping, accuracy is less critical, therefore we can use a broader fleet of satellites to capture images. These images are lower in resolution. In GIS terms, our mapping products are DSMs.

For a list of deliverables, see PhotoSat’s Satellite Mapping Products and Options.

  • Alteration Mineral Mapping: Using spectral analysis, PhotoSat identifies specific types of altered minerals in a target area. Exploration geologists use altered mineral maps when selecting targets for advanced mining exploration.


For more information, see Alternation Mineral Mapping.


Does PhotoSat offer a DTM?

Yes. Our elevation surveys are DTMs. See Satellite Surveying.  

Does PhotoSat offer a DEM?

Yes. Our elevation surveys start as DEMs. During processing, we remove ground features like trees or buildings. Our final deliverables are DTMs. 

Does PhotoSat offer a DSM?

Yes. Our satellite mapping services produce DSMs. See Satellite Mapping.