Miatapower List Archive

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Mail From: John Suchak <(email redacted)>

Hey Gang-

Here's the response from the Ask-A-Cop guy about the capabilities of
modern rolling radar. It seems that we're not safe from the long arm of
the law no matter what. (sigh...)

Moral of the story, as Eric pointed out, is that there's no substitute
for knowing what's around you before running it up to triple digits.
(And, apparently no substitute for being a cute girl once you get pulled
over!)

Here you go:



Ask A Cop wrote:
>
> John
>
> The following is an excerpt from my Visitor Questions page (page 1)
> concerning Radar and Speeding:
>
> "The radar unit is able to determine the target vehicle's speed by
> sending out two separate beams, called "high-" and "low-doppler" signals.
> The low doppler strikes the roadway in front of the patrol vehicle and
> reflects back to the radar unit to determine the speed of the patrol
> vehicle. At the same time, the high doppler is sent out, strikes the target
> vehicle, and reflects back the closing speed between the patrol and target
> vehicles. The radar unit then determines the target vehicle's speed by
> calculating the difference. For example, if the low doppler determines that
> the patrol speed is 50 and that the closing speed with the target vehicle is
> 110, it subtracts the patrol speed from the closing speed and, in this
> example, displays the target speed of 60."
>
> While some moving radar units are connected to the patrol car's speedometer,
> it is normally only to help to eliminate "ghost readings" by "matching" the
> patrol's speedometer to the doppler signal's findings. While the actual
> formulas used to determine the speed of same direction moving targets get
> pretty complicated, I can assure you that the technology is indeed in use
> and is very effective and credible in court.
>
> I hope this has helped. If I can be of further assistance, please let me
> know.
>
> Kevin
>
> users.firstva.com/askacop
>
> ----- Original Message -----
> From: John Suchak <(email redacted)>
> To: <(email redacted)>
> Sent: Monday, August 14, 2000 1:41 PM
> Subject: Dear Officer...
>
> > Sir:
> >
> > A discussion regarding Police Radar has popped up on our Miata mailing
> > list and I'm hoping that you can help us settle a disagreement.
> >
> > Here's the question:
> >
> > Can radar be used to establish the speed of a vehicle moving in the same
> > direction as the Police cruiser? I am of the understanding that the
> > vehicle mounted radar units are somehow connected to the cruiser's
> > speedometer and therefore *can* extrapolate the "targeted" vehicle's
> > actual road speed. A fellow list susbscriber contends that in such a
> > scenario the radar is only capable of measuring the difference in the
> > target and cruiser's speeds. (Note that this question pertains to the
> > "permanently mounted" radar units, not the handheld units which clearly
> > have no connection to the cruiser's speedometer.)
> >
> > The same person is also contending that radar is ineffective when the
> > cruiser is in motion at all, as "background" objects like trees and
> > buildings will give false readings (returning the cruiser's speed as the
> > radar reflects off them..).
> >
> > I believe that the gentleman making these assertions is operating under
> > a bit of a misconception, and would appreciate any assistance you may be
> > able to provide regarding the subject.
> >
> > Thanks for being "on the job".
> >
> > John Suchak