Simply point the camera crosshairs at the horizon; check the shape of the Earth!
Not sure what shape Earth you live on? Check whether the horizon is at 90 degrees to the vertical to see if we are on a flat Earth!
You can also log the position of sky objects by pointing the crosshairs at an object and taking a screenshot.
Check the promo video! https://www.youtube.com/watch?v=07tdfyWvTG4
I have fixed the issue with Android 6... now it requests camera and location permissions at startup the first time as required. If you had "Camera not found" errors before this should fix it.
NOTE: The app is tested on Nexus 5 and 7 only so far. It should work on any phone with a camera and orientation sensors.
Copyright Aaron Dover / Concentricity Limited 2015.