Arccos features a built-in GPS function that will automatically give you the distance to the front, middle, and back of the green you are playing. Tap the location arrow near the top right hand corner to view this GPS screen.
To activate the enhanced rangefinder function during a round, tap and hold anywhere on your phone's map screen to reveal the rangefinder beacon. Once it appears, you can drag the beacon to any point on the screen; this will give you the distance to that point, as well as the distance from that point to the center of the green. This is handy for exact distances to hazards, or to determine the best location for layup shots.