Text 394, 214 rader
Skriven 2004-08-24 12:54:48 av mark lewis (1:3634/12)
    Kommentar till text 388 av Michiel van der Vlist (2:280/5555)
Ärende: Fido on the move via cell phone.
========================================
 >>  >> The problem with that theory is that they can't tell if
 >> >> there's PAM on the plate until they see the video.

 >>  MvdV> The problem with your theory is that the PAM does not
 >>  MvdV> work on the European reflector plates.

 >> how do you know unless you've tried it?

 MvdV> I haven't tried it personally but I know of people who did.
 MvdV> And I know odf people who did some tests under laboratory
 MvdV> condition.

you can list these people for outside contact regarding this and their test
results are available for the public?? did they use the same PAM formula that
is available in the US??

 MvdV> It doesn'r work. It is urban legend.

TTBOMK, too many have used it over here and gotten away with it for it to be an
urban legend...

 >> are the european reflector plates (and other things based on
 >> the same "technology" like road signs) not based on the crushed
 >> glass particles in paint stuff that north american stuff is
 >> based on?

 MvdV> What I do know is that the plates are much better reflectors
 MvdV> than the road signs.

probably due to colors used... white is better than others at reflecting...
even moreso when laced with crushed glass crystals ;)

aside: over here, we have some sign makers that use vinyl for the sign
content... they lay everything out on a computer a then the vinyl is cut by a
CAD plotter type of device that uses a cutting blade instead of pens... this
vinyl is available in many colors and reflectivity... i've made reflective
signs for folks to put on their vehicles, homes, and in their yards...

 MvdV> If you think about it for a minute you will know that it can
 MvdV> not work. The give away is the claim that one can not see it
 MvdV> withthe naked eye.

the claim is "one cannot see the PAM residue [...] with the naked eye"... that
makes a huge difference...

 MvdV> Over here they use visible light for the camers. So if the
 MvdV> naked eye can not see it, the camera can't either.

its not that simple... the cameras are also geared to look at certain
frequencies of light ;)

 MvdV> Maybe the cameras in North Amrica use infrared. Then it just
 MvdV> /may/ work/. In theory. I doubt it though. I suspect Roy is
 MvdV> feeding us urban legend too.

some remote cameras use "visible", infrared, and ultraviolet technologies...
some use a mix or only one or two...

 MvdV> Have you actually tired it yourself? If not how do yo know it
 MvdV> works?

i've never had a need to... i've not ever been in an area that uses those
(illegal) cameras... i say "illegal" because over here, they are owned by
private companies and the tickets are issued by private companies... not the
police...

 >>  MvdV> Those and the pure passive devices that only give a warning
 >>  MvdV> when it detects a radar trap, are illegal too. When they see
 >>  MvdV> you avoid speed traps by slowing down when in range of them,
 >>  MvdV> they chase you and stop you. And they start looking. Don't
 >>  MvdV> think you can fool them by hiding the thing. They know what to
 >>  MvdV> look for and they will find it.

 >> that would indicate that there are live cops around
 >> watching and "profileing"...

 MvdV> There are. Not at every autonatied speed trap of course, that
 MvdV> would defeat the purpose of automation. But they do spot
 MvdV> checks.

must be between doughnuts OB-)

 MvdV> Also some stretches are watched by cameras. The cops are in a
 MvdV> building somewhere else, but they can send cops on fast
 MvdV> motorcycles after you if the detect suspicious behaviour.

if what detects suspicious behavior? talk about "big brother"... geez...

 >>  >> Doesn't work very well with the laser light
 >>  >> units though.

 >>  MvdV> Does not work at all with the laser guns. Period.

 >> that would depend on one's distance from the gun ;) the
 >> beams aren't so constricted as to still be a few mm's in
 >> cross section at 1/8th mile ;)

 MvdV> /Radar/ detection devices don't work on laser guns. Period.

hahahaha... tell that to my radar detector ;) it catches'em when they are
aiming at me from any angle... does a good job, too... not that i've ever
needed the detector for that purpose...

 >>  MvdV> What helps is a "laser shield" but they are illegal too
 >>  MvdV> and as the laser gun speed traps are operated manually
 >>  MvdV> they will see immidiately when your are using one. Again
 >>  MvdV> they will chase you....

 >> again, those are manned stations... the original thread was
 >> about the automated, speed triggered cameras ;)

 MvdV> And then someone mentioned laser guns...

right... some systems also use lasers in their detections...

 MvdV> Those are always manned.

lack of knowledge == ignorance ;)

 MvdV> The laser must be pointed at the car you want to trace.
 MvdV> They usually point them at th licence plate as it is a
 MvdV> good reflector...

no, they only needed to be pointed at a specific target zone and will then work
with anything that enters that zone and reflects their beam back... any
reflective surface will work... we don't have front mounted plates in all
states... FWIW: i've only ever lived in one state that did...

 MvdV> The laser guns are used on very busy spots where an automatic
 MvdV> radar trap would not work because it can't tell which car in
 MvdV> the crowd is speeding.

yes, and its for "up close" work, too... at 1/8th mile (201m) or 1/4th mile
(402m), the beam is quite large in diameter...

hummm... here's an interesting device...

===== snip =====

Laserpro 904

How does LaserPro work?
=======================
First, a brief introduction on how police laser speed guns work. Laser speed
guns measure the speed of their target using the time-of-flight principle.

They send out a train of laser pulses and receive the return signals reflected
off your car. The time it takes between the laser pulses going out and coming
back is recorded. This time-of-flight measurement reveals your distance from
the laser gun.

Consecutive measurements of your distance over a period of time, typically 3
seconds, gives the information on how your distance is changing, i.e., your
speed. LaserPro confuses the speed calculation by sending "echo" pulses into
the laser gun between its own pulses.  The remote-mount laser unit
(transceiver) has both a photo diode (detector, receiver) and a laser diode
(transmitter, emitter). When the detector "sees" the first pulse from the speed
gun, it triggers the laser diode to fire back a pulse train, but at a much
higher rate than that of the laser speed gun. Since the laser wavelength in
both devices are the same, LaserPro's signal is accepted by the gun. The
computation of speed is then delayed because the laser gun receives information
it considers inconsistent. This lasts for seven seconds while you are warned by
the dash-mounted control panel. This five second delay is long enough for you
to slow down if necessary.

After firing, the bumper-mounted transceivers will shut down and recycle for
one minute while you clear the speed trap, after which time it will be ready to
function again.

===== snip =====

the above device is listed at 259.99 pounds... i guess that's british monetary
pounds...

one site on the internet quotes

[quote]"Why shouldn't I trust my radar/laser detector to protect against laser?

Laser detectors are ineffective for two reasons: First, the laser beam from the
speed gun is very small, about four feet in diameter at the normal targeting
range."[/quote]

"normal targeting range" is defined as 500-1200 feet... lessee, that'd be
152-365 meters distance... still, 4feet in diameter at normal trageting range!
damn... its surprising that they get enough light reflected back to detect...
yes, it does make it a bit harder for the detectors to catch the beam aimed at
another vehicle and warn you but then again, some detectors are sensitive
enough that they will warn you further out than "normal targeting range"...
they only need to detect light in that bandwidth to sound the alarm... since
the laser gun can detect it, the laser detector should have an easier time
since 1) its not a reflected signal and 2) its not as scattered as what the gun
would be trying to detect...

i won't even mention that a driver that is properly observant should be able to
see a police car that may be laser targeting before they get into range...

then, there's stuff like this...

===== snip =====

I've passed a zillion camera's & my RD hasn't gone off once, what's wrong?

Serco, the official distributor & installer of Gatsonometer's speed cameras
have indicated that only 1 in 8 cameras (12.5%) is ever operational at any one
time. Our own testing has confirmed the same with the exception of London which
has a 3 in 8 live ratio (37.5%) & Scotland which has a rather high 6 in 8 (75%)
live operation ratio. Although a camera may not be operational one day, the
next day the police may choose to load it with film.

===== snip =====

)\/(ark

 * Origin: (1:3634/12)