From: randy@ninja.megatek.uucp (Randy Davis)
Subject: Re: Photo Radar
Reply-To: megatek!randy@uunet.uu.net
Organization: Megatek Corporation, San Diego, California
Date: Tue, 18 Aug 1992 20:33:52 GMT

In article <1992Aug18.190405.20770@linus.mitre.org> cgates@mitre.org (Curt Gates) writes:
|In article <3965.2A913ABD@kennel.FIDONET.ORG> john@kennel.FIDONET.ORG 
|(John Hamilton) writes:
|> would the judge have thrown the
|> case out, asked Mr. Bob to hand the ticket to me, or what?
|
|Nobody will ever know.  Most highway radars indicate the highest speed in 
|its field of view.

  COMPLETELY WRONG...  ALL speed measurement radars indicate the speed of the
STRONGEST return signal, if they indicate any speed at all, NOT the "highest"
speed.  There is no guarantee, or any reason to feel sure at ALL, that the
strongest return signal will be from the nearest vehicle, although that *is*
often the case if all vehicles in the "beam" are of similar microwave
reflectivity.  The nearest vehicle will not be the strongest return signal
in many cases, though, such as a motorcycle with a semi tractor behind it.

  No speed measurement radar measures the distance to the vehicle, anyway.
Note that the laser systems are not, technically, "radar" - the laser systems
DO, however, measure distance and measure speed based on the amount that
the distance changes over time.  All speed radar (which are microwave) measure
the shift in the frequency of the reflected radio signal, which is a direct
measurable result of the speed of the reflecting object either toward or away
from the radio source, and convert that shift into a speed reading which is
displayed..

|  If there is more than one vehicle in view, the officer 
|has to determine which vehicle is going at that speed.

  And therein lies the problem which I have been the victim of myself.  The
officer CAN'T determine which vehicle is going at that speed with 100%
certainty, unless that is the ONLY vehicle moving (and there are instances
where even that can be in dispute).  I've been nailed once with radar, when
I *KNEW* the asshole was there (he deserves this label due to his later
conduct) because my radar detector had been going off for three blocks, and
I was going 10 UNDER the speed limit before that anyway - in my car on a 35
mph street (and in first or second gear, which, because of the heat at the
time, had my fan clutch locked up and making a bit of noise).  There was
a Suburban speeding by at the same time.  Guess which vehicle has a
greater radar reflection between an old-body-style RX7 and a Suburban.

  But nooooo....  *I* was closer...

|  Some cops are 
|careful about how they set up their trap, so it sees only one vehicle at a 
|time.

  Some cops are fucking idiots, too.  It is not possible to setup a trap
so that it ONLY, and in EVERY instance, sees only one vehicle at a time in
such a way that he can measure that vehicle's speed with a radar gun.  The
average beam width of a radar gun is in excess of 5 degrees, which at
a distance of over 200 feet can easily encompass a bike and a semi truck
a half mile behind...  Guess which gives the stronger reflection?

|  Other cops are not as careful.  When it is your word against that of 
|an the officer, guess who a judge tends to believe.

  No debate there - the judge will almost always believe the officer, no
matter how stupid the officer is.  Luckily, not ALL officers are that
stupid, but the stupid ones are the ones you are more likely to be exposed
to...

Randy Davis				UUCP: randy@megatek.com
ZX-11 #00072 Pilot			      megatek!randy@uunet.uu.net
DoD #0013			 	      ucsd!megatek!randy