How does it work?
Radar transmits on what is close to microwave frequency (X, K and Ka band), with each having advantages and disadvantages. Ka provides the best overall performance. This beam is usually 12 degrees wide.
The unit transmits a wave and, once reflected off a MOVING surface, the waves are either compressed (target is closing) or expanded (target is moving away). This wave change is called "Doppler shift". A great example is a car going by with it's horn blasting or a train going by- the sound is unchanged on-board, but rises then falls as it passes.
In Moving radar, a second wave is sent (called "Low Doppler") to determine the speed of the patrol car/motorcycle. Just what you would figure; this Low Doppler simply bounces a wave off the pavement and does the same math to determine speed of the patrol car. The two signals' (Low and High Doppler) delta determines the target speed.
LIDAR works a bit differently; a timed pulse of infrared light is transmitted and reflected by the target. This pulse goes out and is timed for its return; some simple math determines the speed toward or away from the unit. At 1000', the beam is about 3.5' wide. There is no Moving LIDAR... yet.
Both units measure the speed of the target towards the unit- this provides a "cosine error" unless the target is headed directly towards (or away from) the unit. This error is on the side of the target (that is, is to the advantage of the target- reading a slower speed than actual); the greater the cosine error, the greater the advantage to the target. To illustrate, imagine going down a six lane freeway (three lanes each way), a 1/2 mile out there is only 1-3 degrees of error; but up close, at say 100 feet, the error is significant.
POP, Instant on, Alarms and Thresholds have been prohibited by the IACP as they disallow for some necessary radar testimonial evidence.
The operator (in California) needs to have completed a 24 hour class (a six hour add-on for LIDAR) to qualify in its use. Any cop can show you how to use one- you'll be picking out targets in under 5 minutes... this stuff is good, really good- and in the hands of an expert user; get out your license and press hard.
Yeah, yeah:
-this is me talking, not that of any law agency, manufacturer, court or otherwise.
- all this info is in the public domain.