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Sample Form

Compute Mininum Range

The form below computes the range between a target and a moving radar for a given acceleration (mph or kmh per radar sample time) due to the Cosine Effect. Other calculated parameters include time to target even with radar, relative (measured) speeds, and speed error. Except for Distance (2) and Acceleration (5), all numbers entered must be whole numbers (no decimal point).
FORM input image

NOTE: Radar angle to patrol car direction does not effect the measured target acceleration component; the alignment does effect radar measured patrol car speed which in turn effects measured target speed.

Sample Form Results

Cosine Effect Acceleration
moving-mode radar

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 		0 degrees65 mph
105 kmh

Cosine Effect
ACCELERATION 		RANGE TIME to
Even		 Speed
Measured		 Speed
Error
1 mph / 250 ms
1.6 kmh / 250 ms 		188 feet
57 meters		 1.03 sec 58 mph
93 kmh		 -2 mph
-4 kmh
234 feet
71 meters		 1.28 sec MINIMUM to start Track
and complete a full cycle
before Cosine Effect >=
1 mph per 250 ms

The above table applies to radars tracking approaching targets. The table applies to receding (going) targets by replacing Time to Even (with radar) with Time FROM Even; also MINIMUM to start Track (start point of last track period) would become ending point of first possible track.

In the above example (60 mph target, 65 mph radar 35 feet off target path) targets have a Cosine Effect acceleration component of 1 mph per 300 milliseconds (1 mph/300 ms) at about 188 feet (1 second) from target even to radar. The closer the target the greater the acceleration component. A radar with a sample time of 300 ms cannot measure targets traveling at 60 mph and 188 feet or closer to the radar (minimum range 188 ft for a 60 mph target) because speed is changing too fast (1 mph/300 ms or greater).

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Police Traffic Radar Handbook
Chapter 4.3