I keep an amateur insect collection and sometimes I use iNaturalist to help me identify tricky specimens. The easiest way for me to do this is by taking pictures with my smartphone through a microscope and adding them to an observation. INaturalist then pulls the incorrect GPS coordinates from my photo of the pinned specimen and there is no option for me to manually enter the correct GPS coordinates. I have to approximate the location by moving the pin on a map. I realize that I could send the photos to a computer and then use the iNaturalist website which does have a GPS field, but if this field were in the app too it would greatly simplify things.
In decimal degrees?
Yes, I think that would be the most convenient format.