Speed Measured by RADAR

Posted Wednesday, October 25, 2017 by Andrew Charles Huff

RADAR stands for Radio Detection And Ranging, and is a general term for determining the range, angle, or velocity of objects. Modern traffic radar uses the Doppler effect, which is an increase or decrease in the frequency of waves traveling between an observer and an object. Light also travels using wavelengths and this is how law enforcement officers measure speed.

When measuring for speed, a Trooper will typically use an SMD to direct a beam of light toward an object. The SMD measures the time it takes for the beam to be reflected back to the device. This split-second measurement tells the Trooper the object’s estimated speed.

Law enforcement officials typically measure speed in three different scenarios: while stationary on the side of a roadway, while in a moving motor vehicle, or from an overhead aircraft.

While stationary, an officer will simply aim an SMD at the vehicle to detect the actual speed and confirm their suspicion.

If an SMD is mounted in a moving motor vehicle, the device will measure the difference in speed between the moving police or patrol car and the suspect vehicle. The device will then attempt to calculate the true groundspeed of the suspect vehicle.Vehicle speed can also be measured and enforced by a stopwatch or GPS mapping system in overhead planes.