Google camera prompts about saving location on first startup. Graphene's default camera defaults to "off".
I naively assumed, given how GPS works, that I could enable location access, and disable network access for the camera app, and that it would still be capable of copying two floating point numbers from the local GPS chipset to the exif data.
Instead, it wants to call out to some questionable network services.
I'm clearly not the only one that wants this feature. Graphene even includes a reimplementation of the necessary Google API.
However, it (and the original google implementation) are flaky. This all "just worked" on my iPhone and (before that) Windows Phone. It didn't even occur to me that it was a thing that could be screwed up.