I guess my question is "naive". I get from https://images-api.nasa.gov some pictures of Earth from ISS without any description (just the mission number) or pictures of crewmembers.

Taken with a DSLR device, are these pictures actually geolocalized (or space-localized?)? I mean: I suppose GPS Satellites signals cannot reach ISS, so do astronauts take notes from each taken picture? or is there a software which converts pictures timestamps to space localization?

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    $\begingroup$ GPS works great at ISS; it is the primary source for position and attitude information. space.stackexchange.com/q/2320/6944 $\endgroup$ – Organic Marble Nov 21 '20 at 19:27
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    $\begingroup$ Geolocate moon pictures? There was no GPS back then and it doesn't reach out to the moon anyway. $\endgroup$ – Loren Pechtel Nov 22 '20 at 3:38
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    $\begingroup$ @LorenPechtel, GPS isn't the only way of doing geolocation. The locations of the various lunar surface pictures have been determined to very high precision through photogrammetry. Apollo-era photogrammetry determined the locations to withing 1.5 meters (better than bare GPS); a modern re-calculation determined the positions with sub-meter accuracy. $\endgroup$ – Mark Nov 22 '20 at 4:25
  • $\begingroup$ Mind splitting your "relative question" out into its own post? It's an interesting question that deserves its own answer. $\endgroup$ – Mark Nov 22 '20 at 4:32
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    $\begingroup$ @OrganicMarble While GPS works at space-station altitude, consumer electronics GPS receivers like those you'd find in a camera or phone probably won't because of firmware speed and altitude restrictions $\endgroup$ – Dragongeek Nov 22 '20 at 21:41

In actuality it works like this:

The location of the ISS at the time Earth photos are taken by the US ISS crew is calculated by the ground. The process is called 'Crew Earth Observation' and it's described here:

.. crew members use commercial and professional digital handheld cameras with a suite of lenses (from wide angle to a 1200 mm lens equivalent) to take Earth observation photographs that support research in a wide variety of Earth Science sub-disciplines. Scientists on the ground train the crew in basic areas of Earth system science and provide the crew a daily list of targets of the greatest scientific interest. Crew members take these photographs as time is available and during their leisure time. These digital photographs are downlinked, and both images and meta-data (especially lens used, moment the image was taken, and nadir point of the ISS) are assimilated into a public database.

(emphasis mine)

Source: Crew Earth Observations NASA page

In sense, however, GPS is used, because the position and attitude of the ISS is calculated using GPS.

The images are available to the public at the Gateway to Astronaut Photography of Earth.

Here's an example from there, showing a very muddy Galveston Bay flowing into the Gulf of Mexico after all the flooding from Hurricane Harvey, with the nadir point and photo center point indicated.

enter image description here

The part about Apollo photography should be split out into its own question IMHO.

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    $\begingroup$ There's nothing better than a "how it actuality works" answer. +1 $\endgroup$ – uhoh Nov 22 '20 at 1:34
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    $\begingroup$ @organic-marble Thx for this "gateway" link. I noticed, however, some pictures are not geolocalized. And a lot of them miss photo center point. Is it manually added by ground staff? $\endgroup$ – david Nov 22 '20 at 7:55
  • $\begingroup$ @david yes, manually added, and the process quoted above is only for the CEO project; that gateway has pictures from many other sources including Apollo, shuttle, ISS non-CEO, etc. $\endgroup$ – Organic Marble Nov 22 '20 at 11:35
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    $\begingroup$ It is indeed a very manual process. I've seen pitches before about trying to attach some sort of orientation sensor to the ISS cameras to better nail down what's being pointed at, but I don't think anything suitable was ever found, nor was anything toward that end ever funded. $\endgroup$ – Tristan Nov 23 '20 at 19:50
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    $\begingroup$ Prior to the pandemic, I had a little photo game played in the break room in my work area where I would print out interesting earth observation photos I found on IO and have people guess where it is (not before determining it myself, of course). Once you do a bunch of them, you start to have a good feel for what different cities (and even rural parts of various countries) look like. $\endgroup$ – Tristan Nov 23 '20 at 19:54

If a camera is equipped with a GPS receiver and stores a valid location together with the image when used outdoors on Earth, this will not work in the ISS.

The ISS blocks the reception of GPS signals of GPS antennas inside the metallic walls.

If a GPS signal is received occasionally through a window, the civilian GPS will not work at such a speed and height. The GPS needs to "see" more than only one satellite through the small window. So the only way to geolocalize pictures taken from the ISS is to do it like described in the other answers. But a time offset of only 0.5 seconds may cause an error of some km. Camera clocks are not designed to be set with milliseconds precision.

The ISS is fast, the orbital speed is 7.66 km/s, the ground speed is a little bit slower, 7.2 km/s. If the time error is about 0.5 seconds, the position is off by 3.6 km, not bad for an image with a diagonal of 86 km taken with a 200 mm lens from a distance of 400 km. But on Earth the position error is only about 10 m.

The Apollo Missions could not use a navigation satellite. But many manual surface photos were localized on maps afterwards.

enter image description here

Small part of this Source.

This Apollo 12 map indicates the camera position and direction by the four digit underlined image numbers with the arrows.

The planimetric maps created by Brian McInall in 2014-7 from Lunar Reconnaissance Orbiter Camera photos and re-examination of the Hasselblad images.

The map was generated more than 40 years later using modern images as well as modern computer hardware and software. At the time of the Apollo mission such a map was possible only using a lot of manual work.

Automatic orbit photos taken by a camera unit in the Service Module were referenced with position data. The circle indicates a panoramic series of photos. The localized photos are to be found here.

  • $\begingroup$ So, you mean that whatever GPS coordinates seen on official sites, they are not trustworthy? "some km" means : +/- 100 ? +/- 1000? $\endgroup$ – david Nov 22 '20 at 7:48
  • $\begingroup$ @david which official sites and coordinates are you referring to? $\endgroup$ – Tim Nov 23 '20 at 18:15

Partial answer to

Are pictures taken from ISS geolocalized?

Yes, if the astronauts keep the clocks inside the DSLRs set properly (and I'm guessing that they will definitely do this!) then the location of the camera can be reconstructed easily. What the camera is pointing at is a different question. The camera can be virtually geotagged, but not the subject.

GPS inside the ISS

I'm pretty sure that it's going to be extremely difficult for a commercial GPS unit inside a handheld camera held by hand inside of a big tin can (Faraday cage) called the ISS will pick up enough signals from enough GPS signals at any given moment for that unit to register a fix.

It might happen once in a while, but not in a regular, reliable way.

Yes answers to Does GPS work at ISS? and other GPS Q&A here indicate that the beam patterns from some GPS satellites intentionally cover an area slightly larger than earth and so there's an annulus around Earth's disk as seen from space where bright "flashes" of GPS signals will appear.

However there are several differences between GPS positioning by a spacecraft and by a simple commercial hand-held device.

Commercial units have firmware restrictions on both altitude and speed to make them COSPAR-friendly.

Commercial units require simultaneous captures of at least four satellites to get a meaningful position from space, (if they weren't self-blocking for reasons described above). Fancy space GPS can play tricks and record fixes from different GPS satellites at different times and reconstruct a trajectory with an orbit ephemeris and them back-calculate a position at a given epoch. DSLRs can't do that.

This would require the camera "seeing" all around the edge of the Earth's apparent terminator, which means you might have to hold the camera in very specific positions fairly close to the cupola's central window. The signals come from all around the edge of the huge looming Earth disk, not from the ground.

"Virtual" geotagging

...is there a software which converts pictures timestamps to space localization?

I'm no expert, but I assume that ISS photographers keep the clocks in the cameras set properly. The orbital history of the ISS is well known and documented, so all it takes is reading the timestamp in a given historical image's metadata and some historical TLEs and one can find the position of the camera to a few kilometers.

What the camera is pointing at is a different question. The camera can be virtually geotagged, but not the subject.

  • $\begingroup$ Can on-board cameras use directly GPS signals received by ISS? with a wire or wifi? $\endgroup$ – david Nov 22 '20 at 8:00
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    $\begingroup$ @david that's a great question to ask in Photography SE or Internet of Things SE! There are all kinds of location protocols for interior or other spaces where GNSS signals aren't readily receivable. Maybe there's something like that inside the ISS and in (at least some of) the DSLR camera bodies up there. Great question! $\endgroup$ – uhoh Nov 22 '20 at 8:06
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    $\begingroup$ "if the astronauts keep the clocks inside the DSLRs set properly", ugh, that's bad enough I joined just to complain. Cheap GPS receivers (yes, even the ones in high-end cameras are "cheap") assuredly aren't accurate enough to know the time to the precision needed for GPS. They get the time from GPS. Read through the answers here and here. $\endgroup$ – Matthew Nov 23 '20 at 19:36
  • $\begingroup$ @Matthew I'm not sure of your point yet. My position is that handheld devices inside a metal container with windows that only face towards Earth only 400 km below receive no useful GPS signals at all. Time stamping is the only way to recover later where the camera was when the photo was taken, and that can only happen if there is a clock in the camera, not associated with GPS in any way, is set properly. If you have some information that says those cameras do receive useful GPS signals it will be great to hear about and please consider posting that information in an answer. $\endgroup$ – uhoh Nov 23 '20 at 21:39
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    $\begingroup$ Ah, I see... it wasn't obvious to me that you were talking about geolocating based on the known position of the ISS at a given time; I thought you were saying that GNSS requires an accurate clock. That said, a camera with occasional access to one GPS satellite might still use it to set the time. I'd still expect the camera timestamps to have a fair margin of error, though, possibly on the order of seconds, as it's hard to do better a) if you're setting a clock by hand and b) with the limited internal accuracy precision that is likely present on such devices. $\endgroup$ – Matthew Nov 24 '20 at 14:24

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