I need to know the field of view of the camera of the phone to make an augmented reality app, for calculate where i have to write on the camera view the name of a gps located Point of interest of a city on the correct coordinates of the screen, pointing the point of interest.
for example:
distance 5 meters: 6 meters (from left to right FOV)
distance 10 meters: 12 meters (from left to right FOV)
How to calculate it?