Speed camera calibration

GPS_fan · Posted: Tue May 22, 2007 8:11 am Post subject: Speed camera calibration

After searching the forum I couldn't find anything so, at the risk of ridiculing myself, I'd like to pose this questions:

does anybody know the procedure(s) for calibrating speed cameras?

can speed camera accuracy be affected by things such as weather conditions - rain, mist/fog, bright sunlight?

Static cameras all appear to have lines painted in the road to verify the speed indicated by a camera and there are lines painted where temporary (and some mobile) cameras are placed - but there are no such markings for the majority of mobile sites.

How can we be sure of the accuracy of a speed camera when there is no secondary system for verification and/or photographic evidence of the speed displayed on a handheld unit.

I'm not asking this as a habitual speeder, but from previous experience in the pharmaceutical industry, where equipment has to be calibrated to the nth degree and documented accordingly.
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Andy
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Darren · Posted: Tue May 22, 2007 8:49 am Post subject:

I can't speak for all but GATSO's are 'supposed' to take two images a fixed time apart. It is from these that speed can be calculated by measuring the distance covered between the first and second image.

However there has been some concern about the calibration as an independent survey found the timings varied and even small differences here can result in a large error in speed calculation.
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Darren Griffin

GPS_fan · Posted: Tue May 22, 2007 9:35 am Post subject:

Thanks Darren,

I thought I'd seen something to that effect.

...if there's concern over the timing between two photos taken with a Gatso, I would have thought this would make the accuracy of readings from handheld units even more questionable

I wouldn't like to ask for documented evidence of calibration though if I got caught because, with my luck, they'd probably just throw the book at me
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Andy
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Darren · Posted: Tue May 22, 2007 10:56 am Post subject:

When I was serving we only had handheld radar and these were calibrated every morning with a tuning fork designed for the purpose. I've no idea how a Laser unit is calibrated but suspect it has to be sent to the manufacturer. AIUI, calibration isn't the issue with handheld laser, it's the spurious readings that can be picked up that cause the problems.
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Darren Griffin

MaFt · Posted: Tue May 22, 2007 12:31 pm Post subject:

i saw a program a few months back about the validty of mobile camera readings - the main issue they were presenting was how the laser 'spreads' over distance - even on recently calibrated units. so even if the laser was perfectly targeted to the car in question it would spread enough to pick up speeds from other vehicle's nearby and mess up the readings.

as another person who has worked in pharmaceuticals and all the calibration and documentation required i think it'd be looked at differently in the case of speed cameras. people don't eat speed cameras (usually) so the calibration is not 'life-threatening' - alright, it's a bit rubbish of you get caught b a 'dodgy' camera but it won't kill you like a dodgy drug might!

MaFt

mrgrimsby · Regular Visitor Joined: Mar 05, 2007 Posts: 147

Darren said "when I was serving" what do you mean? Where you a waiter? Please dont tell me you used to be a plod!!!!
I don't BELIEVE IT!!! Darren you are full of suprises. Laughing

Darren · Posted: Tue May 22, 2007 8:11 pm Post subject:

I was indeed a Police Officer, 13 years service before injury led me to a new career in computers Smile

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Darren Griffin

GPS_fan · Posted: Wed May 23, 2007 7:45 am Post subject:

A few interesting comments.

I wasn't expecting it to be a good enough reason to be let off - it was more curiosity, especially in light of their apparent/possible increasing numbers.
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Andy
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Darren · Posted: Wed May 23, 2007 7:59 am Post subject:

I am normally (and understandably) on the side of the Law in such matters but a number of reports and discussions about the calibration and general accuracy of the equipment has left me rather unsettled.

Sadly, unless you can afford an expert to question the accuracy there is little hope of being aquitted Crying or Very sad

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Darren Griffin

GPS_fan · Posted: Wed May 23, 2007 8:42 am Post subject:

...and the more you try to put forward a defence, the harder they come down on you.

so the 'law' wins when Joe Public just decides to take it on the chin
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Andy
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