Speed camera 38 mph too fast!
Discussion
From today's Daily Telegraph:
"
A motorist who received a fixed penalty notice saying a camera had caught his van travelling at 51 mph in a 30 mph zone has had the penalty overturned after the film showed he had been driving at only 13.42 mph.
Kris Haskins, deputy mayor of Portland, Dorset, was told to pay a £60 fine within 28 days or face prosecution but demanded to see the film from the camera.
Dorset Speed Camera Partnership cancelled the penalty notice after admitting that the camera's radar had been triggered by a reflected image.
Mr Haskins, 36, an electrician, said he feared other drivers might have been victims of the same error and had not challenged the fine and three penalty points.
"I was fuming when I received the notice," he said. "I knew it was wrong but thought there was no way I could prove it. Then I found out through a friend I could request to see the pictures the camera took.
"I went back to the scene and worked out that I only travelled three metres between the two pictures. When you convert that back it equates to 13.42 mph."
The Dorset Speed Camera Partnership said in December that 23,733 drivers had been fined in the eight months to March 2003, raising more than £1.4 million.
A spokesman said there had been two similar cases in Dorset in the past year.
'A reflected image occurs when a radar detects a movement that isn't actually there, which is caused by distortion or a shape of a stationary vehicle. A reflection can occur where the radar reads two images as one.
'This is an extremely rare occurrence and is a known radar phenomenon.'
"
Humm! Two cases in around 24,000 (say), that's 1 in 12,000. Not what I would call "extremely rare"! And those cases are the known ones. What about all the others where the 'victim' took it on the chin and didn't check.
It's clear, you should always ask for the evidence.
Streaky
"
A motorist who received a fixed penalty notice saying a camera had caught his van travelling at 51 mph in a 30 mph zone has had the penalty overturned after the film showed he had been driving at only 13.42 mph.
Kris Haskins, deputy mayor of Portland, Dorset, was told to pay a £60 fine within 28 days or face prosecution but demanded to see the film from the camera.
Dorset Speed Camera Partnership cancelled the penalty notice after admitting that the camera's radar had been triggered by a reflected image.
Mr Haskins, 36, an electrician, said he feared other drivers might have been victims of the same error and had not challenged the fine and three penalty points.
"I was fuming when I received the notice," he said. "I knew it was wrong but thought there was no way I could prove it. Then I found out through a friend I could request to see the pictures the camera took.
"I went back to the scene and worked out that I only travelled three metres between the two pictures. When you convert that back it equates to 13.42 mph."
The Dorset Speed Camera Partnership said in December that 23,733 drivers had been fined in the eight months to March 2003, raising more than £1.4 million.
A spokesman said there had been two similar cases in Dorset in the past year.
'A reflected image occurs when a radar detects a movement that isn't actually there, which is caused by distortion or a shape of a stationary vehicle. A reflection can occur where the radar reads two images as one.
'This is an extremely rare occurrence and is a known radar phenomenon.'
"
Humm! Two cases in around 24,000 (say), that's 1 in 12,000. Not what I would call "extremely rare"! And those cases are the known ones. What about all the others where the 'victim' took it on the chin and didn't check.
It's clear, you should always ask for the evidence.
Streaky
i defo would consider 1 in 12000 extrememly rare, but agree that you shoud always inspect the pic if poss. don't forget that the other 11999 *may* well have actually been speeding (amazing but true ..!) in which case it's a fair cop..
it's a shame the system isn't 100% foolproof though ..
it's a shame the system isn't 100% foolproof though ..
joospeed said:"Extreme" - "situated at the farthest possible point from a center". The centre in this case being the 'norm'. "Rare" - "seldom occurring or found". One in millions could be "extremely rare", one in tens of thousands is (IMHO) not.
i defo would consider 1 in 12000 extrememly rare, but agree that you shoud always inspect the pic if poss. don't forget that the other 11999 *may* well have actually been speeding (amazing but true ..!) in which case it's a fair cop..
it's a shame the system isn't 100% foolproof though ..
tuscan_thunder said:
supposedly battering a tennis ball past does the same thing.
fairly pointless i know
A mate from school used to be able to serve at over 100mph, would be funny practicing his serve in a 30 Pointless depends wether you vote for BRAKE or SAFER?
At the end of the day the camera is there saying "I am here, so you better drive SAFELY", it just can't nick anyone cause its film is full of tennis balls
>> Edited by knowley on Wednesday 7th January 12:00
knowley said:
Ah, so does this mean the myth about setting off cameras with a tin can attached to a peice of string might be true?
Yes
You just need to find out the minimum size of tin can to trigger the camera (radar cross-section).
Although if you can lay your hands on a suitable microwave gunn unit on the right band and...... it's a lot less effort
Le TVR said:
You just need to find out the minimum size of tin can to trigger the camera (radar cross-section).
Although if you can lay your hands on a suitable microwave gunn unit on the right band and...... it's a lot less effort
LOL! You tried it then?
Minimum size, so this could be larger than a single normal sized tin can?
Mircowaves set off speed cameras?... best be watching out for speeding ready meals then
knowley said:
LOL! You tried it then?
:fifthamendmentmode:
I'm saying nowt....
:/fifthamendmentmode:
knowley said:
Minimum size, so this could be larger than a single normal sized tin can?
The smaller the can the closer you need to be to the detector for the same effect.
knowley said:
Mircowaves set off speed cameras?... best be watching out for speeding ready meals then
Your microwave oven is operating around S band (2.5GHz). The GATSO is probably on Ka band, approx ten times higher in frequency. However Ka band gunn units / motion detector etc can easily be found surplus. Just adjust the frequency until the detector is triggered every time you point at it.
All depends how intelligent your GATSOs are with the return radar signals.
Le TVR said:
:fifthamendmentmode:
I'm saying nowt....
:/fifthamendmentmode:
The smaller the can the closer you need to be to the detector for the same effect.
Your microwave oven is operating around S band (2.5GHz). The GATSO is probably on Ka band, approx ten times higher in frequency. However Ka band gunn units / motion detector etc can easily be found surplus. Just adjust the frequency until the detector is triggered every time you point at it.
All depends how intelligent your GATSOs are with the return radar signals.
Great Stuff.... so if you don't want to stand too close to the camera whilst u spin a can on string, don't cut the can into smaller pieces.
And re the microwave stuff... your saying that a Gatsos frequency to high to cook ready meals?
HEHEHEHE
Le TVR,
You seem to know about these things so you might appreciate a design for a device I drew up in the eighties, but never had the guts to actually build. It was an X Band cavity modulated or pulsed through a 555 timer at about 1KHz which happens to be the Doppler heterodyne frequency for a 30MPH return when clocked by a hand held X band gun. My logic was that the directly transmitted 1000KHZ would swamp the front end of the radar gun so that it would be unable to read the echo from my car. If it didn't drive it into saturation it would give 30MPH on the nail - every time!
You seem to know about these things so you might appreciate a design for a device I drew up in the eighties, but never had the guts to actually build. It was an X Band cavity modulated or pulsed through a 555 timer at about 1KHz which happens to be the Doppler heterodyne frequency for a 30MPH return when clocked by a hand held X band gun. My logic was that the directly transmitted 1000KHZ would swamp the front end of the radar gun so that it would be unable to read the echo from my car. If it didn't drive it into saturation it would give 30MPH on the nail - every time!
streaky said:
Humm! Two cases in around 24,000 (say), that's 1 in 12,000. Not what I would call "extremely rare"! And those cases are the known ones. What about all the others where the 'victim' took it on the chin and didn't check.
It's clear, you should always ask for the evidence.
Streaky
If there are 3 million tickets to be issued this year, 1 in 12,000 (1 in 8000 if there were two other cases?), this means that between 250 and 400 people will get speeding tickets for not speeding! Innocent till proven guilty? Ha!
streaky said:
Humm! Two cases in around 24,000 (say), that's 1 in 12,000. Not what I would call "extremely rare"! And those cases are the known ones. What about all the others where the 'victim' took it on the chin and didn't check.
It's clear, you should always ask for the evidence.
Streaky
If there are 3 million tickets to be issued this year, 1 in 12,000 (1 in 8000 if there were two other cases?), this means that between 250 and 400 people will get speeding tickets for not speeding! Innocent till proven guilty? Ha!
When manufacturing radar intruder detectors in the eighties, we used a device called (by us) a Doppler wheel to set up our microwave movement sensors. These sensors are very similar to the Doppler devices used for Gatsos. The wheel we used was a small plastic fan shaped like a water wheel. That is, it had paddles about 15mm square arranged around the circumference of a disc of diameter of no more than 120mm. These paddles were metallised by gluing aluminium foil on to the paddle surfaces. The wheel was driven by a small electric motor taken from a cassette deck and it looked to the detector, from about a couple of metres down an anechioc tunnel like a man sized target at about 50 metres range. Any kind of rotating turbine-like structure with, preferably, metallic blades, rotating at an appropriate speed, held up immediately in front of the camera's detector should be able to trigger the device at any speed you choose. The peripheral velocity of the blades is what you need to calculate.
motco said:
Le TVR,
You seem to know about these things so you might appreciate a design for a device I drew up in the eighties, but never had the guts to actually build. It was an X Band cavity modulated or pulsed through a 555 timer at about 1KHz which happens to be the Doppler heterodyne frequency for a 30MPH return when clocked by a hand held X band gun. My logic was that the directly transmitted 1000KHZ would swamp the front end of the radar gun so that it would be unable to read the echo from my car. If it didn't drive it into saturation it would give 30MPH on the nail - every time!
That's one way. Did some work with sweep modulation on X and Ku band gunn units. Triggered every time. Max sweep was several MHz. Which translates as
:hanssolo:
Give me lightspeed Chewy..
:/hanssolo:
Le TVR said:
Le TVR,
You seem to know about these things so you might appreciate a design for a device I drew up in the eighties, but never had the guts to actually build. It was an X Band cavity modulated or pulsed through a 555 timer at about 1KHz which happens to be the Doppler heterodyne frequency for a 30MPH return when clocked by a hand held X band gun. My logic was that the directly transmitted 1000KHZ would swamp the front end of the radar gun so that it would be unable to read the echo from my car. If it didn't drive it into saturation it would give 30MPH on the nail - every time!
Did some work with sweep modulation on X and Ku band gunn units. Triggered every time. Max sweep was several MHz. Which translates as
:hanssolo:
Give me lightspeed Chewy..
:/hanssolo:
I really like the simplicity of swamping the front end with the (audio range) signal - but these cameras do something to distinguish between approaching and receeding traffic.
One must assume that the audio range signal from mixing source and return from an approaching car is rejected as a possible trigger condition.
How do they do that?
And would the same mechanism reject the swamping audio signal?
Best Regards,
Paul Smith
Safe Speed
www.safespeed.org.uk
Funny that, the device we made was variously known as a stereo Doppler, or direction sensing. It had a pair of Schottky diodes arranged in the Rx cavity, equally disposed about the local oscillator which was in its turn bled through from the Gunn Tx diode. The two detectors rectified out a LF signal in quadrature, the phase realtionship of one to the other gave the direction information. Marconi et al made similar devices but we made our own at the time. These days, the costs of achieving the necessary PTT and radio authority certificates would make it better to buy something off the shelf; a stripline design, perhaps? I cannot say without some time to think, what would happen if the device was bombarded with an audio frequency modulated signal of the same fundamental frequency as the Tx. As it is not related to the Tx oscillator it's likely that it would be rejected as common mode interference. We did have problems with LF reflections from fluorescent lights etc., though, although these were common mode. The signal processing that detected the phase information needed a bit more refinment, IMHO. Nothing over about about 150Hz was processed because we were looking for man targets, not vehicles. We did make a special unit for a stately home; it detected approaching cars at night and illuminated a sign warning of roaming deer in the park. false activations weren't a problem, though!
Safespeed: How do like a device that was offered to "celebs" in LA called "Flashback"? It was a device mounted on a hat and comprised a flash tube and a light sensor. If a paparrazo fired off a flash gun at the "celeb", the flash unit on the wearer's hat flashed back instantly thereby grossly overexposing the photographer's shot. Could this possibly have another application? 
safespeed said:
I really like the simplicity of swamping the front end with the (audio range) signal - but these cameras do something to distinguish between approaching and receeding traffic.
One must assume that the audio range signal from mixing source and return from an approaching car is rejected as a possible trigger condition.
How do they do that?
And would the same mechanism reject the swamping audio signal?
Best Regards,
Paul Smith
Safe Speed
www.safespeed.org.uk
The doppler shift of the reflected signal will either be positive or negative depending on the direction of the target. The receiver could easily process on the correct shift for the direction of trafic.
Similarly an intelligent unit could only accept signals if the shift was:
- between certain limits (no impossible speeds or multipath reflections)
- relatively stable in shift (not interference)
- on one single received carrier (multiple reflections)
Of course they may be quite 'dumb' too.
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