Speed Camera / Slippage Help required

[echo]

justinp1 said:

You probably could! But could you form an opinion of speed before you lamped them?

justinp1 said:

On a serious note, contrary to popular belief it is not only the reflective number plate which will return the laser beam. The tiny amount of light they need to get a 'reading' means that most objects will, thus the operator has no idea which parts of the car was targeted from that distance, and to a certain extent *which* car! At 400m, 2mm of hand shake will move the beam 2.4m which would be into the other lane of traffic.

Try going out at night and shining a torch at a parked car - the light reflected from the plate will be by far the brightest thing on the car you can see well at any distance. It's not that the plate is the only reflective thing - it's that the number plate is the only thing that is designed to reflect light back towards the source.

[justinp1]

smeggy said:

justinp1 said: The tiny amount of light they need to get a 'reading' means that most objects will, thus the operator has no idea which parts of the car was targeted from that distance, and to a certain extent *which* car! You are right - to an extent. The laser beam will not show up on the video (the IR pulses are far too short). Hence the gun should be checked at the start of each tour of duty to ensure the laser beam is correctly aligned within the crosshairs (in both the vertical and horizontal planes). Always request the full video evidence

Unless its a handheld device which means that you have to just trust that they didnt move or get blown by the wind 2mm...

[smeggy]

echo said:

justinp1 said: On a serious note, contrary to popular belief it is not only the reflective number plate which will return the laser beam. The tiny amount of light they need to get a 'reading' means that most objects will, thus the operator has no idea which parts of the car was targeted from that distance, and to a certain extent *which* car! At 400m, 2mm of hand shake will move the beam 2.4m which would be into the other lane of traffic. Try going out at night and shining a torch at a parked car - the light reflected from the plate will be by far the brightest thing on the car you can see well at any distance. It's not that the plate is the only reflective thing - it's that the number plate is the only thing that is designed to reflect light back towards the source.

At least you can see where the (continuous) light from your torch is shining; you’ll have a bit more trouble with these invisible nanosecond laser pulses (as will any camera).

[smeggy]

justinp1 said:

smeggy said: The laser beam will not show up on the video (the IR pulses are far too short). Hence the gun should be checked at the start of each tour of duty to ensure the laser beam is correctly aligned within the crosshairs (in both the vertical and horizontal planes). Always request the full video evidence Unless its a handheld device which means that you have to just trust that they didnt move or get blown by the wind 2mm...

You might be right. I can't dispute that because I've never seen this procedure being done.
Has anyone?

[justinp1]

smeggy said:

justinp1 said: smeggy said: The laser beam will not show up on the video (the IR pulses are far too short). Hence the gun should be checked at the start of each tour of duty to ensure the laser beam is correctly aligned within the crosshairs (in both the vertical and horizontal planes). Always request the full video evidence Unless its a handheld device which means that you have to just trust that they didnt move or get blown by the wind 2mm... You might be right. I can't dispute that because I've never seen this procedure being done. Has anyone?

From the evidence given in my trial, the PC used the device handheld from 400m. In cross examination he said that a 1 or 2mm movement was not just possible but inevitable. I would tend to agree.

[echo]

smeggy said:

At least you can see where the (continuous) light from your torch is shining; you’ll have a bit more trouble with these invisible nanosecond laser pulses (as will any camera).

You don't need to 'see' - the laser gun's electronics does the 'seeing' (faster than you can blink)

[justinp1]

echo said:

smeggy said: At least you can see where the (continuous) light from your torch is shining; you’ll have a bit more trouble with these invisible nanosecond laser pulses (as will any camera). You don't need to 'see' - the laser gun's electronics does the 'seeing' (faster than you can blink)

And then the laser guns electronics shows you a precision picture of the exact point the light waves were hitting, and does a print out of the number plate, whilst automatically moving the pulse to a flat face of the target and holding there for the 1/3 second on a 70mph vehicle?

I think not! But our BiB are expected to!

[justinp1]

echo said:

smeggy said: At least you can see where the (continuous) light from your torch is shining; you’ll have a bit more trouble with these invisible nanosecond laser pulses (as will any camera). You don't need to 'see' - the laser gun's electronics does the 'seeing' (faster than you can blink)

Another point, seeing implies recognising what you are hitting with light. No device does that, just reports a speed and distance of an area approximately in the centre of crosshairs which are *not* directly linked to where the light has been sent/returned from.

[smeggy]

justinp1 said:

echo said: You don't need to 'see' - the laser gun's electronics does the 'seeing' (faster than you can blink) Another point, seeing implies recognising what you are hitting with light. No device does that, just reports a speed and distance of an area approximately in the centre of crosshairs which are *not* directly linked to where the light has been sent/returned from.

This being my point! Unless the crosshairs check is done (correctly), you wont know where the beam struck! The torch analogy is erroneous.

[justinp1]

smeggy said:

justinp1 said: echo said: You don't need to 'see' - the laser gun's electronics does the 'seeing' (faster than you can blink) Another point, seeing implies recognising what you are hitting with light. No device does that, just reports a speed and distance of an area approximately in the centre of crosshairs which are *not* directly linked to where the light has been sent/returned from. This being my point! Unless the crosshairs check is done (correctly), you wont know where the beam struck! The torch analogy is erroneous.

The second problem is even if the crosshairs check is done, you still dont *know* where the beam hits as it makes no mark, as per se a bullet of a gun would mark. Something I mentioned in court to a firearms trained officer was that if we asked anyone who has taken a pistol shot if they had hit the target, they would say yes. After all, have lined up the crosshairs exactly and pulled the trigger. If it were that easy though, anyone could do it. As we know even though that is where we are aiming, some (most) of the time it does not hit the intended target, the difference is with a pistol shot you can see the mark on the target. With a laser beam we have to guess, and of course the guess is going to be the car it was aimed at...

[simond001]

A question to all,

is it worth my while arguing the point, or should I just put up and pay up!

I have since my visit to the police station sent the following.

"Afternoon Jill,

I am really struggling to understand the photographs.

Would it be possible to advise me of the numbers shown (nr33 and 43) and the timeframe that is used for these. Also please could you advise the relevance of the cross hairs on my car. On one photo they are directly on the S in my number plate, but on the other lower and to the left of the S. Is this correct?

I know that I am running out of time to get this solved, so would really appreciate your help in advising the meaning of the photo's. I have received a letter refusing to send me the calibration information, also advising that the courts may well increase my fine if I do not accept this.

Kinda scary, but if you could get this back to me by email, as the letter also states I must comply within the 28 days."

Jill, the lady at Northants Police is very sympathetiv to my plight, and is struggling to gain any information for me. It appears that my local police station are a lot more approachable for info than her force.

Kinda enjoying this, but still do not want 3 points for an offence that i am not happy i committed.

Also interesting to note that independant calibration on my speedo is irrelevant, as is my word, whereas the Serco calibration and word are deemed true.

What ever happened to an Englishman's word is his bond?

[smeggy]

simond001 said:

Would it be possible to advise me of the numbers shown (nr33 and 43) and the timeframe that is used for these. Also please could you advise the relevance of the cross hairs on my car.

http://pepipoo.com/Case_Files/documents/CF11_LTi2020_screen.htm

simond001 said:

On one photo they are directly on the S in my number plate, but on the other lower and to the left of the S. Is this correct?

This doesn't mean anything; you should not fight it on that basis (the 2nd pic is only for driver ID).

Post both pics, perhaps we PHers can spot an abnormality

[echo]

justinp1 said:

Another point, seeing implies recognising what you are hitting with light. No device does that,..

Agreed hence my inverted commas around 'see'

justinp1 said:

..just reports a speed and distance of an area approximately in the centre of crosshairs which are *not* directly linked to where the light has been sent/returned from.

This is the real point that some others on here seem to be missing:
The cross hairs have nothing to do with the point on the 'target' that is measured - they are just there to show the viewer the approximate centre of the area being targeted.
The point on the 'target' that is measured will be the point with the brightest reflection and this can happily move relative to the gun and/or the crosshairs with no impact on the accuracy of the reading - ie you can wave the gun around (a little ) and so long as the brightest reflection within the field of view of the reciever stays the same point on the target then bob's yer uncle.
You don't need to be a 'sharpshooter' (good job too with the guys who use them ).


My torch analogy is just to show how easy it is for the device to distinguish between the bright reflection from the plate and any other reflections from bodywork etc.

[smeggy]

echo said:

……… The point on the 'target' that is measured will be the point with the brightest reflection and this can happily move relative to the gun and/or the crosshairs with no impact on the accuracy of the reading - ie you can wave the gun around (a little ) and so long as the brightest reflection within the field of view of the reciever stays the same point on the target then bob's yer uncle.

That is wholly incorrect!
Lidar guns are not very sophisticated. They will ‘lock on’ to the nearest surface where the beam reflects, not the brightest. Therein lies the problem. Its electronics needs a while to carryout interpolation processing and settle for the next measurement.

Lasertech.com said:

If the receiver is detecting energy back from several surfaces, it will calculate the range to the nearest one.

echo said:

My torch analogy is just to show how easy it is for the device to distinguish between the bright reflection from the plate and any other reflections from bodywork etc.

It can’t.
Unlike your 2 analogue 130 megapixel eyes driving a powerful signal processor, the Lidar gun uses a one pixel imager which drives a simple comparator.

[echo]

enough for me now

[LongQ]

Just thought I would have another look at the LTI site (www.lasertech.com) to see if there is any fresh information forthcoming from that source.

Got as far as the second screen and saw them claiming this

"All speed lasers ARE NOT created equal. Our technology has held up in court hundreds of times and has not lost a case due to the laser's inaccuracy. Can any other laser manufacturer say that?"

Soooo, they are claiming the Ultralyte has never lost a case (though I seem to recall its forerunner did) but that all the competitors kit is flawed and cases have been lost.

Interesting. Would be fun to refer to that in court if one was ensnared by one of the others.

I wonder if we could bounce that claim of a competitor to see what they come back with?

[justinp1]

LongQ said:

Just thought I would have another look at the LTI site (www.lasertech.com) to see if there is any fresh information forthcoming from that source. Got as far as the second screen and saw them claiming this "All speed lasers ARE NOT created equal. Our technology has held up in court hundreds of times and has not lost a case due to the laser's inaccuracy. Can any other laser manufacturer say that?" Soooo, they are claiming the Ultralyte has never lost a case (though I seem to recall its forerunner did) but that all the competitors kit is flawed and cases have been lost. Interesting. Would be fun to refer to that in court if one was ensnared by one of the others. I wonder if we could bounce that claim of a competitor to see what they come back with?

I think that this is known in an abeit different strand of the legal system as 'salesmans puff'.

Analysing *exactly* what they say, they say it has held up on hundreds of cases. I would like to see if they actually had any data to support that claim. It also says that it has never lost a case due the laser's inaccuracy: I guess the ones they did lose were down to operator error or improper use!?

It also says that the technology has held up in court hundreds of times: This would not be too difficult as they do not release any information about how the inaccuracy trapping software works!!! (Due to industrial and trademarking reasons apparantly)

It is hard to lose a case about a subject only you know about and you are not forced to release the details about!