I have heard that a picture such as the one Bob put is is actually, maybe, thousands of tiny pictures. These are then assembled by a computer, with the error detection code and considerable AI components. BTW, they are not even transmitted in colour (grayscale) but are colourized by the programme based on instrument data from the surface!
While I am not au fait with the actual system used, something I have seen and been able to gather important information from are the scanning lasers to produce a "cloud" 3D model. The "model" is not physically comprised of faces, vertices, chamfers, fillets, etc. like I used to make in Autocad in order to produce moulds for, amongst other thing, Colgate toothbrushes, telephones or shampoo bottles, but is instead a collection of georeferenced points, think of millions of surveyors marks.
Rgds.
Dave
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