radar guns work on the principle of doppler shift. You send out an EM (radar) pulse of a certain frequency and measure the frequency of the one you get back. Using the frequency difference, you can calculate the speed difference between yourself and the object that reflected the wave. Police radar guns CAN now be integrated/plugged into the cars so that they make use of the car's speed to determine yours, rather than relying on the cop's judgment of how fast he was going when he tagged you. However, this is not uniform, so you may want to lookup the radar gun type info and check whether that is the case. Of course, if the cop was sitting still when he tagged you. . . that issue is moot. |