Ahh I get it (I think). overlaying a grid on the camera feed... to show lat/long.
well, I imagine you'd have to draw a normal ole grid on the correct axis (z? been a while since i've done opengl..), and somehow draw that on the camera output. you'd also have to detect tilt of the device and change the opengl viewport accordingly, so the lines "stick" to the earth on the camera output. interesting concept, let us know how you go