GPSTC Speed Detection Operator Practice Test

The significant cause of the Cosine Effect in stationary RADAR is when the antenna is pointed across the road or at an angle to the target's path. This phenomenon occurs because the RADAR measures the speed of a target by calculating the change in the frequency of the reflected signal as it bounces back to the unit. When the antenna is aimed directly at the target, the measurement is accurate, as the full speed of the vehicle is being detected.

However, when the antenna is angled, the speed that the RADAR calculates is affected by the cosine of the angle between the RADAR beam and the direction of the target's movement. If the angle is not zero, the speed reading will be lower than the actual speed of the vehicle. This effect is known as the Cosine Effect, as it can be mathematically expressed using the cosine of the angle, leading to a distortion in speed measurements. Understanding this is crucial for proper speed enforcement, as inaccurate readings can result from improper antenna alignment.