But the location of the camera doesn't matter. You only need to figure out very roughly at which latitude you are to know by how much to compensate for earth ro

But the location of the camera doesn't matter. You only need to figure out very roughly at which latitude you are to know by how much to compensate for earth rotation. And you can do that with the sensors that you're already using to do the stabilisation. That was my point... no need for GPS.