Wow. Just read this thread for the first time. Don't know how I missed it. Some good info here. Nice job Alan breaking down the various law enforcement dectection methods.
However.................
I'm waiting for the, "your full of shit, everything you said is all wrong, and the -- but you forgot/missed" contingency to check in first. :lol:
I am up!!!! :lol:
You incorrectly describe LASER (LIDAR) as being a doppler measuring device. LIDAR doesn't measure doppler frequency shift, but uses the old fashioned time/speed/distance calculations. Using the speed of light that the pulse is traveling, it measures the time it takes to hit the target and return to calculate a distance. Then compares that distance with the distances calculated from repeated pulses to calculate the target's speed. I know. I am splitting hairs.
Although you mentioned it in a later follow-up post, it is important to remember that the Radar Detector Detectors that the police use cannot pinpoint which car has a radar detector. (Unless of course you are the only car around or you give it up by hitting the brakes when the radar goes off) And they are used widely not only as a tool in states where radar detectors are illegal, but also in commercial vehicle enforcement as it is federal regulation that commercial vehicles are prohibited from using radar detectors.
VASCAR. I am only familiar with one unit, but it is much more flexible than you describe. It is a mobile unit in that the distance measurement is done by the LEO "on the fly" using his police car and for any distance of his choosing. It could be a quarter mile, or it could be several miles. He doesn't have to be 90 degrees. He simply starts the timer when the target passes a reference point. He then starts the distance calculator when is police car passes that same distance point. Later, he stops the timer when the target passes a second reference point, and then stops the distance calculator when his police car passes that same second reference point. So almost always, the police car operating VASCAR will be traveling in the same direction as the target, and behind it.
Instant on and laser will give you no useful warning.
For the most part, all police radar in use these days is "instant on". You can get useful warnings when police are using instant on radar, but not always. The key is that the instant on radar needs to be activated on another target in your vicinity and your detector picks that up before you become the target. It may be only a faint signal that comes and goes quickly, but if its K or especially Ka band, SLOW DOWN! Now even with instant on radar, the LEO has the choice of just leaving it on or activated which makes our job a hell of a lot easier. But if it's a disciplined LEO using instant on, or you are the only vehicle around for miles, then yes, your eyes better identify the threat before it identifies you!
3) Radar guns, except for Lidar, focus on the largest moving object in your proximity. Last summer I had a local LEO notice me once too often and he started trying to zap me with radar whenever he saw my blue bike. Every time, there was a car or truck nearby and, even though I was even passing the truck one time, he could not get a fix on my speed. He did give me the 'slow down' sign as I passed him.
There are several variables affecting which target the radar will identify, but distance from the radar gun, or antenna, is the single biggest factor, not size of the target. Size would be second. And with today's new fancy-schmancy radars, the LEO can direct it give the speed of secondary, or faster targets. So in your example, if the LEO had a modern radar it's quite possible that he did get an accurate reading on your speed and just decided it didn't hit his threshhold for action.
Good discussion folks!
