My guy doesn't know anything about how GPS works

Not suitable for this.

GPS is a purely one-way method, with the satellites transmitting only their position and a timecode, leaving the receiver to do the triangulation. And if they did send any sort of custom data packets over that method, it would just confuse the crap out of every other receiver across most of the world, causing potential device crashes, drawing attention from ham operators worldwide...

And also massively pissing off the US military. Turns out a lot of their equipment and munitions make use of GPS and INS, so fucking with those satellites is a no-go.

And? Tell me you have no idea what GPS is or how it works.