Hand held laser speed guns - how accurate over 150 m?
Discussion
Was pulled over the other day by a pair of BiBs doing 48 in a 30 zone. They showed me the reading and sthe display said the reading was taken at 485 feet (147 m) away.
My question is, how accurate is a hand held device over this sort of distance? I have been back to the site and at that distance, a 911 is a pretty small target.
I don't mind too much paying the £60 FPN - but a bit concerned as to how they can be sure it was my car they were lasering at that distance.
My question is, how accurate is a hand held device over this sort of distance? I have been back to the site and at that distance, a 911 is a pretty small target.
I don't mind too much paying the £60 FPN - but a bit concerned as to how they can be sure it was my car they were lasering at that distance.
johnfm said:
Was pulled over the other day by a pair of BiBs doing 48 in a 30 zone. They showed me the reading and sthe display said the reading was taken at 485 feet (147 m) away.
My question is, how accurate is a hand held device over this sort of distance? I have been back to the site and at that distance, a 911 is a pretty small target.
I don't mind too much paying the £60 FPN - but a bit concerned as to how they can be sure it was my car they were lasering at that distance.
My question is, how accurate is a hand held device over this sort of distance? I have been back to the site and at that distance, a 911 is a pretty small target.
I don't mind too much paying the £60 FPN - but a bit concerned as to how they can be sure it was my car they were lasering at that distance.
147m is about the shortest I have heard of!
I showed in court that to hit a number plate at 400m away, which was what I was supposedly targeted at needs a medal winning pistol shooting performance at the last olympics!
In Peter Ward's thread he is being prosecuted at over 800 metres!
So, in a nutshell, the size of the target at that distance is fine - the issue is whether the reading is accurate. It is perfectly possible at that distance to encounter, or indeed induce 'slip error' - something which has been shown in independant testing.
justinp1 said:
In Peter Ward's thread he is being prosecuted at over 800 metres!
745.5m actually. "When I die, you shall find 745.4m engraved on my heart"
you think a car looks small at 147m? A car is smaller than the laser scatter at 745.4m, but the LTI's still completely accurate, and anyone who thinks otherwise can't be given a copy of the complete session video just in case he's right -- sorry, how silly of me, it's simply because it's "not in the public interest [to show how poor the results really are?]".
Peter Ward said:
justinp1 said:
In Peter Ward's thread he is being prosecuted at over 800 metres!
745.5m actually. "When I die, you shall find 745.4m engraved on my heart"
you think a car looks small at 147m? A car is smaller than the laser scatter at 745.4m, but the LTI's still completely accurate, and anyone who thinks otherwise can't be given a copy of the complete session video just in case he's right -- sorry, how silly of me, it's simply because it's "not in the public interest [to show how poor the results really are?]".
I was caught at 601m and I thought I'd drive up a road, get out and walk back 600m - the car was tiny so how they got a valid reading from that distance (handheld with no tripod) I don't know. And as has been mentioned, the evidence of this is never released - my conclusion therefore is that the CPS and all those in it are c**** and I hope they all suffer long painful deaths due to some horrible venereal disease, although this implies they are having sex with someone/something. They have no idea/don't care what is in the public interests. Ahem,....
fatboy b said:
First thing I'd ask is why the BiB were doing 48 in a 30! 
Very witty! I was allegedly doing 48 in a 30 - though how you are supposed to know its a 30 zone is intriguing - but I doubt lack of speed signs between where I pulled on to the main road and when I was lasered would be a defence.
johnfm said:
fatboy b said:
First thing I'd ask is why the BiB were doing 48 in a 30!
Very witty! I was allegedly doing 48 in a 30 - though how you are supposed to know its a 30 zone is intriguing - but I doubt lack of speed signs between where I pulled on to the main road and when I was lasered would be a defence.
Don't be so sure about that as a defence, nip over to pepipoo to check, but I think that improper signage of a limit change can be a defence.
johnfm said:
..though how you are supposed to know its a 30 zone is intriguing - but I doubt lack of speed signs between where I pulled on to the main road and when I was lasered would be a defence.
You're correct, a lack of signage would probably not be a defence..(ETA - bear in mind I'm not aware of the road in question, mind)
If there is a system* of street lighting spaced not more than 200 yards (183m apart), and unless a specific order has been made or the road is signed to the contrary, then its a 30mph limit. Repeater signs cannot be placed along such a road - see The Traffic Signs Regulations and General Directions 2002.
(* system = 3 or more lamps, IIRC)
Edited by SS2. on Monday 21st May 16:21
Peter Ward said:
justinp1 said:
In Peter Ward's thread he is being prosecuted at over 800 metres!
745.5m actually. "When I die, you shall find 745.4m engraved on my heart"
you think a car looks small at 147m? A car is smaller than the laser scatter at 745.4m, but the LTI's still completely accurate, and anyone who thinks otherwise can't be given a copy of the complete session video just in case he's right -- sorry, how silly of me, it's simply because it's "not in the public interest [to show how poor the results really are?]".
My bad Peter, I had the figure mixed with another similar case.
For clarification, on NSL roads it is usually the case wherever possible the 'vans' seem to zap at 500-800 metres away - as far as they can possibly get a reading without error.
On residental roads these are often 'policed' at much closer proximity, handheld, which seems to be the case here.
My case was in between, I think only because of the unusually long and straight dual carriageway he had the time to zap at 400m away and drive down off the overbridge and catch up.
I think there are two separate but linked possible errors which can take place. Dr Clark has shown that at 100-200m the beam can slide down the sides of vehicles with a small derivation in aim creating a consistant 'addition' to the readings which will fool the error trapping.
At the extreme distances I think that the factor seems to be that due to the distance involved and the possibility of misalignment maximised that if a reading is taken from another object it cannot be definately the vehicle aimed at. At these distances the view is visibly shaky - and thus so will the track of the beam, thus lowering the quality of the distance recordings which are used to make up the speed figure. If not enough readings are taken which ally with the prediction of the error trapping the device will produce an error message.
It has often been the case that on the videos of the extreme distances the speed figure often comes before or after or sandwiched by error messages, showing that the 'evidential' figure is taken on the very limit of what may be seen as most likely an error.
As we are not allowed to know where the lime of probably a true reading or an error is set as it is a 'trade secret', we are in the dark.
I think in this case, if the OP is questioning the figure and he doesnt believe he was doing that speed then the former theory of error is the most likely culprit.
smeggy said:
Hughesie II said:
depends on the gun, a pro-laser is much easier to use than an LTI at distance.
Yeah? How so?
personal Experience
www.pistonheads.com/gassing/topic.asp?h=0&t=225869&hw=Hughesiecop
About half way down...
justinp1 said:
Peter Ward said:
justinp1 said:
In Peter Ward's thread he is being prosecuted at over 800 metres!
745.5m actually. "When I die, you shall find 745.4m engraved on my heart"
you think a car looks small at 147m? A car is smaller than the laser scatter at 745.4m, but the LTI's still completely accurate, and anyone who thinks otherwise can't be given a copy of the complete session video just in case he's right -- sorry, how silly of me, it's simply because it's "not in the public interest [to show how poor the results really are?]".
My bad Peter, I had the figure mixed with another similar case.
For clarification, on NSL roads it is usually the case wherever possible the 'vans' seem to zap at 500-800 metres away - as far as they can possibly get a reading without error.
On residental roads these are often 'policed' at much closer proximity, handheld, which seems to be the case here.
My case was in between, I think only because of the unusually long and straight dual carriageway he had the time to zap at 400m away and drive down off the overbridge and catch up.
I think there are two separate but linked possible errors which can take place. Dr Clark has shown that at 100-200m the beam can slide down the sides of vehicles with a small derivation in aim creating a consistant 'addition' to the readings which will fool the error trapping.
At the extreme distances I think that the factor seems to be that due to the distance involved and the possibility of misalignment maximised that if a reading is taken from another object it cannot be definately the vehicle aimed at. At these distances the view is visibly shaky - and thus so will the track of the beam, thus lowering the quality of the distance recordings which are used to make up the speed figure. If not enough readings are taken which ally with the prediction of the error trapping the device will produce an error message.
It has often been the case that on the videos of the extreme distances the speed figure often comes before or after or sandwiched by error messages, showing that the 'evidential' figure is taken on the very limit of what may be seen as most likely an error.
As we are not allowed to know where the lime of probably a true reading or an error is set as it is a 'trade secret', we are in the dark.
I think in this case, if the OP is questioning the figure and he doesnt believe he was doing that speed then the former theory of error is the most likely culprit.
TBH, I probably was doing close to that speed. What irks me is you only know the speed limit on that section of road if you have entered the section from the main road. I pulled on to the main road from a side street, and from where I tuned on to where it becomes a 50 mph zone (ie about 250m) there are no speed limit signs.
johnfm said:
What irks me is you only know the speed limit on that section of road if you have entered the section from the main road. I pulled on to the main road from a side street, and from where I tuned on to where it becomes a 50 mph zone (ie about 250m) there are no speed limit signs.
The fact that you missed my previous post explaining why its illegal to have 30 mph repeater signs in a built up area makes me wonder whether you would have spotted the signs even if they existed
Edited by SS2. on Monday 21st May 17:51
Hughesie II said:
smeggy said:
Hughesie II said:
depends on the gun, a pro-laser is much easier to use than an LTI at distance.
Yeah? How so?
personal Experience
www.pistonheads.com/gassing/topic.asp?h=0&t=225869&hw=Hughesiecop
About half way down...
Wow, that's nothing short of fantastic, nice one Lambocop!
I know people who would pay for an experience like that....... me for one
Do you know that that tells me: the error window for the Pro-laser is much wider - more prone to undetected slip! I don't suppose you tried for it?
rsv gone! said:
Does anybody have a link to the video of that biker who was supposedly clocked at warp factor 1.4 when in fact he was only gaining slightly on the lorries to his left?
If you mean the biker who was clocked at 77 - 78 - 80 - 85 - 107 - 87 (I believe it is referred to as the 'Karl motorbike' video), forget it.
I have already examined the video only to conclude there are absolutely no inconsistencies with the readings (cue several people foaming at the mouth........)
I can't find a link but I can email it if needed.
hi .
My question is where you joined the road for the 250 yards / meter which ever it may be could you see the 50 mph sigh .
would a judge except that that was the only sign on the road and there for advising drivers ie your self of the speed limit as it was in your visitation ?
long shot but what your thoughts .
I feel your pain i got done on a speed camera hand held gun.
I was not speeding as i thought i was approaching accident instead it was a speed trap , and a plastic office waving a gun in the air as he hid behind a post box.
I had to advice of the plastic police man of the correct date . I have requested a copy of the calibration certificate , you got it still today I have not been given a copy of the calibration certificate .which he advised me i would needed to get from the court.
I have been to court and you got it still, no certificate .
A date for trial has now been set.
My father is plod and he can not believe what the plastic has done.
My question is where you joined the road for the 250 yards / meter which ever it may be could you see the 50 mph sigh .
would a judge except that that was the only sign on the road and there for advising drivers ie your self of the speed limit as it was in your visitation ?
long shot but what your thoughts .
I feel your pain i got done on a speed camera hand held gun.
I was not speeding as i thought i was approaching accident instead it was a speed trap , and a plastic office waving a gun in the air as he hid behind a post box.
I had to advice of the plastic police man of the correct date . I have requested a copy of the calibration certificate , you got it still today I have not been given a copy of the calibration certificate .which he advised me i would needed to get from the court.
I have been to court and you got it still, no certificate .
A date for trial has now been set.
My father is plod and he can not believe what the plastic has done.
tomuch said:
hi .
My question is where you joined the road for the 250 yards / meter which ever it may be could you see the 50 mph sigh .
would a judge except that that was the only sign on the road and there for advising drivers ie your self of the speed limit as it was in your visitation ?
long shot but what your thoughts .
I feel your pain i got done on a speed camera hand held gun.
I was not speeding as i thought i was approaching accident instead it was a speed trap , and a plastic office waving a gun in the air as he hid behind a post box.
I had to advice of the plastic police man of the correct date . I have requested a copy of the calibration certificate , you got it still today I have not been given a copy of the calibration certificate .which he advised me i would needed to get from the court.
I have been to court and you got it still, no certificate .
A date for trial has now been set.
My father is plod and he can not believe what the plastic has done.
My question is where you joined the road for the 250 yards / meter which ever it may be could you see the 50 mph sigh .
would a judge except that that was the only sign on the road and there for advising drivers ie your self of the speed limit as it was in your visitation ?
long shot but what your thoughts .
I feel your pain i got done on a speed camera hand held gun.
I was not speeding as i thought i was approaching accident instead it was a speed trap , and a plastic office waving a gun in the air as he hid behind a post box.
I had to advice of the plastic police man of the correct date . I have requested a copy of the calibration certificate , you got it still today I have not been given a copy of the calibration certificate .which he advised me i would needed to get from the court.
I have been to court and you got it still, no certificate .
A date for trial has now been set.
My father is plod and he can not believe what the plastic has done.
no, too far to claim I only saw the 50 mpg sign. I know it is a 30 zone - as I use the road regularly. My point was when I turned onto the road, there is no signage (yes, I know about the lack of repeater signs SS2!)
I will pay the £60 - though my barrister friends assure me it would be 'fun' to go to court and play!! I'm sure it is fun for them, buth then they do this sort of thing everyday in the criminal courts.
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