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Sample Form

Compute Minimum Range

The form below computes the range between a target and radar (includes ladar) 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) speed, and speed error. Target Speed entered must be a whole number (no decimal point).
FORM input image

Sample Form Results

Cosine Effect Acceleration
stationary radar

Target
Speed		 Radar Off
Road (target lane)
60 mph
97 kmh 		35 feet
10.7 meters

Cosine Effect
ACCELERATION 		RANGE TIME to
Even		 Speed
Measured		 Speed
Error
1 mph / 300 ms
1.6 kmh / 300 ms 		120 feet
36 meters		 1.36 sec 58 mph
93 kmh		 -2 mph
-4 kmh
146 feet
45 meters		 1.66 sec MINIMUM to start Track
and complete a full cycle
before Cosine Effect >=
1 mph per 300 ms

The above table applies to microwave and laser 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, radar 35 feet off road) targets have a Cosine Effect acceleration component of 1 mph per 300 milliseconds (1 mph/300 ms) at about 120 feet (1.4 seconds) 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 120 feet or closer to the radar (minimum range 120 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 4.2