Sample Form

Compute Range Given Speed Error

The form below computes the range between a target and a moving radar for a given speed error (due to the Cosine Effect). Other calculated parameters include time to target even with radar, and target acceleration (mph/sec and kmh/sec). Except for Distance (2) and Speed Error (5), all numbers entered must be whole numbers (no decimal point).

NOTE: if target SPEED ERROR less than measured patrol car speed error enter a negative number (-). If measured target SPEED ERROR is positive (+), Radar Angle alignment (theta) must be greater than zero (0°).

Sample Form Results

Cosine Effect Speed Error

Target	Distance Between Radar and Target Paths (lanes)	Patrol Car	Radar Angle off Patrol Car Direction	Radar Measured Patrol Car Speed
60 mph 97 kmh	35 feet 10.7 meters	65 mph 105 kmh	15 degrees	63 mph (-2 mph error) 101 kmh (-4 kmh error)

Cosine Effect
SPEED ERROR RANGE TIME to
Even Speed
Measured Acceleration

-0.5 mph
-0.8 kmh 165 feet
50 meters 0.9 sec 59.5 mph
95.8 kmh 5.83 mph / sec
9.38 kmh / sec

Cosine Effect SPEED ERROR	RANGE	TIME to Even	Speed Measured	Acceleration
-0.5 mph -0.8 kmh	165 feet 50 meters	0.9 sec	59.5 mph 95.8 kmh	5.83 mph / sec 9.38 kmh / sec

In the above example when a target is traveling at 60 mph a radar traveling at 65 mph and 35 feet off target path has a -0.5 mph cosine error when the target is about 165 feet (0.9 seconds) from even with the radar. The closer the target and radar get the greater the cosine error (the lower the radar measured speed).

Police Traffic Radar Handbook
Chapter 4.3