Whilst recognising that this issue is marked solved, to add a note of caution - I have previously relied on Geotag data from the Camera and sometimes found the accuracy unreliable. Unless you have a relatively new phone with fast GPS positioning, you might get variable results (and if your enumerators are using their own phones, add that to the mix).
I would recommend using a Geopoint question directly after each photo capture (I don’t think there is yet a background that can be triggered as specific questions using XLSForm as @Josh says). I know this slows the process down slightly but for the quality of your data, add the question! You can set the visibility of the geopoint question to be dependent on the respective image (use Relevance), so that if the enumerator doesn’t take the nth picture they don’t have to locate the non-existent image…
Worth an experiment - compare the EXIF geotag with the Geopoint information from ODK Collect to see what the variance is (on a decent sample size, more than one phone), and maybe you can decide from there. I’ve found 100m+ differences but that’s on a Samsung Galaxy Note 4 with slow GPS fix - sometimes the camera records the previous location in the geotag even though it indicates a new fix, which is really unhelpful when you download the data!.
Good luck with your project(s)
