This rangefinder(telemeter) measures the Distance to a target by the camera perspective. The effective distance is 10m-1km. To measure the distance, you should know the height(width) of a target.

Don't worry!! Man's height is 1.7m(5.6ft), a golf flag is 7ft, a bus is 3.2m(10.5ft), a door is 2.1m(7ft). With that, we can guess the height of almost everything. It can be very useful to golfers.
Usage is simple: Input the height of the target, and touch the screen. If the target is aligned by 2 lines, get the measured distance.