Images © NASA/JPL/University of Arizona/USGS
First image: Basal Unit and Dunes Location Hi-res JPG
HiRISE DTMs are made from two images of the same area on the ground, taken from different look angles. Not all of these have been made into DTMs due to the time-intensive process. Creating a DTM is complicated and involves sophisticated software and a lot of time, both computing time and human operator time.
The great advantage of a HiRISE DTM is the high resolution of the source images. As a general guide, terrain can be derived at a post spacing about 4 time the pixel scale of the input images. HiRISE images are usually 0.25 – 0.5 m/pixel, so the post spacing is 1-2 m with vertical precision in the tens of centimeters.