Photometric:  These launch monitors utilize a high tech camera system to track the golf ball when struck by your golf club. These units normally sit next to the golf ball. Some photometric units work indoors only and some can be used both indoors and outdoors.Doppler Radar:  These launch monitors utilize a radar system that tracks your golf ball, calculating and estimating the launch conditions. This type of launch monitor sits behind the golf ball and typically needs about 7-10ft of space between the unit and the ball.