Rangefinder: find out the distance to the object

Range finder - designed to determine the distance from the observer to the object.
Principle of operation :
Enter the approximate height at which your phone is located (eye level), point the camera at the point where the object touches the ground. The phone then measures the slope and calculates the distance with simple trigonometry. The angle measures the accelerometer, because The gyroscope may not be in your mobile device.