To use the app as angle finder, make sure your phone is upright. iLevel will automatically transition into the angle finder mode. The picture below shows the main indicators required to measure on surfaces.
The Tilt Indicator
For precise measurements in the angle finder/clinometer mode, your phone needs to be perfectly upright – that means not being tilted forward or backward. To help you with properly setting the tilt, the green tilt indicator show how far forward or back your phone is tilted. Keep it centered at all times.
The picture below shows the tilt indicator (1) when perfectly centered.