Geolocalizing photographs on astronomical bodies

In Are pictures taken from ISS geolocalized? I was considering photos taken on the Moon by astronauts. How can I determine a photographer's position and lens direction?

And further, since there isn't any GPS system around Mars, how are the rovers' exact position determined? (Relatively to their landing bases?)

If we (humans) land on Mars (or any other astronomical body), how can photographs be geolocalized?

• See this question and answer for information about how the Surveyor moon landers were located using photography, especially so that Apollo 12 could land near one: space.stackexchange.com/q/20353/6944 Commented Nov 22, 2020 at 13:29
• It should be noted that even without GPS, latitude and longitude can be determined by utilizing a star-tracker or "digital sextant" and having a view of the night sky similarly to how mariners used to navigate on the open ocean. A good setup can achieve locational accuracy errors below 200m. Commented Nov 22, 2020 at 15:24
• @PeterMortensen see also Why edit other people's posts and undo their use of in-line links? Stack Exchange will automatically display the question title for us when we include the minimal link.
– uhoh
Commented Nov 22, 2020 at 18:35

1 Answer

In general, this is done through photogrammetry: analyzing the positions of objects in the image and comparing them to the positions of those objects in other images. If you have a collection of surface images (eg. the 123 surface photos taken during Apollo 11), you can calculate the relative position and orientation of the camera where each photo was taken; if you can correlate features in the surface images with ones from an orbital image, you can get an absolute position.

With good images, you can get highly accurate relative positions this way: in 1969, the Apollo 11 photos were located to within 1.5 meters; a modern re-calculation produced uncertainties typically less than half a meter.

Other methods can be used (eg. the Mars rovers know how far they've driven and in what directions), but photogrammetry is still used to get the initial position and to correct for accumulated errors.

• I'm always amazed by questions that assume that without GPS you cannot tell where you are. We have been able to tell where we are for 2,500,000 years before GPS went online. When I move around, I usually do not need GPS to know where I am. The vast majority of aircraft don't have GPS, and navigating with map, airspeed, stopwatch, and compass is AFAIK still a mandatory skill for earning a pilot license. Any Boy/Girl Scout will be able to navigate with a map, clock, and the Sun (map optional if you only care about direction). Bees and pigeons can navigate perfectly without GPS. Commented Nov 22, 2020 at 12:10
• So, Lucy could not tell where she was? :) Commented Nov 22, 2020 at 13:30