Recently ISRO released 3D terrain models of Mars' Ophir Chasma terrain as shown here. LiDAR is one instrument which helps in generating such 3D models. ISRO's MARS orbiter sensor payload does not have a LiDAR. Is it using any other instrument or is it calculating the depth information from just aerial images?


There are a couple of ways these can come. In the case of the image you provided, I believe they are using known altitude that comes from MOLA data which accurately found the elevation of the entire Martian surface, and using that to transform the image as it was. They are likely using some terrain features from the image to determine it's altitude as well.

There are two other ways to determine this information. The first is to use shadows to find the relative height of each surface, and appropriately manipulate that to get the right height. The second is to take two images, and use them much as our eyes do to see 3-d. There seems to only be a single image used to create these images, and the shadowing, while I suspect it might be used in part, likely isn't the only thing done with this image.

  • $\begingroup$ MRO stereoscopic DEMs, perhaps? $\endgroup$ – Deer Hunter Aug 21 '15 at 12:31
  • $\begingroup$ Indeed, it looks like Indian Mars Orbiter's pictures draped over MOLA data. $\endgroup$ – Deer Hunter Aug 21 '15 at 12:36
  • $\begingroup$ I suppose the stereoscopic images from MRO could be used, but they are far from global on Mars, MOLA data is global, so... $\endgroup$ – PearsonArtPhoto Aug 21 '15 at 12:39
  • $\begingroup$ stereoscopic images are not possible...if u see the link of ISRO the images are taken from a height of 1857 Km....MOLA data must have been generated with respect to some reference (position of MGS orbitting Mars may be)...how did ISRO align there measurements with that reference? $\endgroup$ – rotating_image Aug 21 '15 at 16:00
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    $\begingroup$ The way they do it is by taking images of the same location at two different times. Satellites move really fast, so that's very easy to do. In addition, Mars doesn't change much from day to day, so using images from two different days wouldn't make much of a difference. HiRISE routinely does this uahirise.org/stereo_pairs.php. If you want to know more about that, feel free to ask another question, as that again is an excellent question. $\endgroup$ – PearsonArtPhoto Aug 21 '15 at 16:10

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