Laser distance, angle & operation
I am trying to find details concerning the optimum distance and operational guidlines for typical (is there such a thing?) police lasers. I recently received an excessive speeding ticket that was way beyond the capabilities of the car. The officer (who was actually a very nice young guy)was sitting in his car, holding the laser in his hand, he stated he had me at a distance of 795 meters, going away from him, and up a very steep hill (with two cars close behind me)
He would have been at least 100feet below me and i am sure his view would have been partially obscured by the other two vehicles. The beam at that distance i believe would have been in excess of 3 meters (10feet?) I am attempting to identify the type of device used but i was told that at that distance the slightest movement of the laser would render inaccurate readings unless the device was on a tripod? Also that typically the police use 500 to 700 feet as an optimum distance for accuracy?
Are there any web based resources to read up on the use, distance, beam width etc?
When you say beyond the capabilities do you mean at a speed greater than the maximum achievable in your vehicle?
Generally cosine angle errors tend to always favor the driver and occur at very close range.
I suppose, though, that given the nature of your description that there may have been sufficient beam divergence--assuming the beam was greater than 8 feet in diameter at nearly 2500 feet away--to have struck one of the other vehicles behind you for a brief period of time and perhaps could have been used in error in inflating what you departing speed was when subsequent readings were taken off of your vehicle.
Perhaps you can mount a successful argument on this front. In my opinion readings taken at that distance with other vehicles in close proximity is a definite no no and likely not in accordance with any proper guideline of laser usage because of beam-divergence errors.
Veil Guy :driver:
795 meters is a fairly long shot but on a departing target, not particularly difficult to make. There's a host of variables that could influence the possibility of incorrect target identification, which is the defense you're proposing. Something produced that target speed; you have a better chance of winning the lottery than proving in court that the laser conjured up the speed all on its own. At least, in 19 years of operating lasers I've never seen it done out on the road.
Before launching into all of these factors, do us both a favor and answer three questions that'll allow me to focus my response and save everyone some time: What target speed did he assign to your vehicle, how close to actual was that speed and was either of the two nearby vehicles traveling at close to that target speed? Without this information, we could waste days with pure conjecture.
Knowing this, I may be able to help you.:)
All speeds and measurements in metric. I was heading up the hill (shown on the picture attached ) and had passed one vehicle on the flat section and another on the rising section before pulling in prior to the passing line terminating (as the officer said, all done correctly with signals etc) He commented to me whilst issuing the ticket that he had me at 80KPH as I was passing the second vehicle and that he ‘gave me' that as I needed to pass safely and get back in prior to the bend. He then stated that I continued to accelerate up the hill before the road curves out of sight, and that he locked on at a speed of 148KPH (the posted speed is 60KPH) When my passenger questioned the officer about the distance the officer retrieved the laser and showed the indicated speed of 148KPH and a distance of 798 meters. I should note that the picture is taken approx half way between the officers hidden car and the 795 meter mark. I am going to take pictures from the officers hiding spot to the 795 meter mark (using a friends laser range finder) and place my car at the exact point along, hopefully, with two other cars behind me to accurately reflect the conditions. The time was 1730 and the sun was very bright at the top of the tree line cresting the hill.
My concerns are, after trying to duplicate the speeds and verifying the performance capabilities of my car, it simply is not possible to accelerate from 80 to 148KPH in the time or distance available before going out of sight. The officer who issued the ticket was the driver of the police car and was hand holding the laser utilizing his other arm as a steadying point. I am looking for answers or pointers to the following:
1.)Is it acceptable/common practice to handhold the laser at distances approaching 800 meters?
2.)Is it possible that slight movement by the officers hand would result in an erroneous reading ? (wide beam divergence)
3.)Would the suns blinding of the laser have any effect?
4.)What is the optimum range officers are trained to operate the laser at?
I will also mention that I am 51 years old and have a clean license, no accidents, no tickets. This section of a new road, which would make a very good F1 track, has become a real cash cow for the police as 99.9% of the tickets issued are for drivers coming down the hill, which requires serious braking all the way to stay within what is generally considered a ridiculously low speed limit. I intend to request a copy of the officers notes for that day and to ascertain how many, if at all, other tickets for 148 were issued. There are other aspects of the ticket that do not meet the legal requirements however I am more concerned with how this speed was ascertained as I know its beyond the cars capabilities in stock form.
As the site's primary admin, I want to be perfectly clear that Craig is merely a member of the forum community as I hope you will continue to be here. He certainly is not a judge, jury, and executioner despite his particular wit, which I suspect has been in part brought on from having fielded many questions from others claiming that they were improperly cited. So please do not take that as a personal, shot, for it was not.
As the Veil Guy had posted in his initial response, 800 metres is quite a distance to get a reading when others vehicles are in such close proximity to the primary target.
With respect to guidelines for proper police lidar operation. The judge from the state of NJ had ruled that police laser shouldn't be operated at distances greater than 1000 feet (300 metres) because of the potential of picking up reflections from vehicles other than the primary target from the beam divergence that takes place. At nearly 2.5 times that distance in your situation, the potential for beam divergence is obviously greater.
Is this something that could have happened in your case, possibly, perhaps if your particular vehicle has a relatively lower laser cross-section than the other vehicles that were close by.
I wouldn't expect a ruling in the USA would carry any weight legally in your country of origin, but knowing about the ruling and the circumstances that its was intended to mitigate, probably can't hurt you in attempting to mount a successful defense.
As Craig accurately pointed out, lighting conditions will only have an affect on range and won't introduce erroneous readings.
I have been able to get faulty readings with panning errors, but only when extremely close to a non moving target (ie; wall) and I trust had would have no potential contribution to creating an erroneous reading, either.
Cosine errors don't sound applicable here either. Cosine errors tend to always favor the motorist, btw.
With respect to whether or not it is common practice, that would largely depend upon where you are. The highest distance I have heard from someone receiving a citation was a shot taken in California at nearly 1800 feet (545 metres).
I hope this helps you mount a successful challenge.
BTW, any idea the model of the police lidar gun used? Was it indicated on the citation?
It would be very helpful if you could find out the make and model of the laser gun that was used.
From the laser guns I have tested, I have never received an incorrect reading. When there is an error, it is reported as an error with no speed indication.
Maybe the laser gun in use is different than the ones I have used and that is why it would be important to know more information regarding the make and model.
What speed do you feel that you actually obtained during this encounter?
What country are you in?
I am attempting to obtain the laser make/model and will advise once i get a response. To answer your questions:
What speed do you feel that you actually obtained during this encounter?
I would estimate, based on my attempts to duplicate the event, between 95 to 100.
What country are you in?
I appreciate the beam width info , could you also answer the hand held at 800 meters? I recall in the early days of Laser they were always on a tripod and i imagine tech advances have allowed some form of steadying software, but as a hunter i know how hard it is to maintain a steady sight at those kinds of distances.
May I ask what part or Province of Canada?
The reason for asking is in the event you are not able to determine the type of laser gun used, others in your area may be familiar with the type of laser used but without your general location, Canada is a big place and what is used in your province may not be what is used in other provinces.
Unfortunately while I sympathize with your situation, a recreation does not always take into account everything that was involved at the time of the original incident. Take adrenalin for example as you had just passed a vehicle. I am not saying you were in the wrong for attempting a recreation; I am merely stating it would be best to have been aware of your speed at the time of the incident as it reflects directly to the point at hand being his recorded speed of 148KPH
Assuming your recreation to be reasonable at 100KPH, this is still a far cry from the 148KPH recorded so there is something still missing from the equation.
Do you know if the car you passed was attempting to catch back up to you for a game of cat and mouse? If so and you were doing 100KPH, he would have had to been going faster to close the gap on you.
I recall that early police lasers were not successful at working thru glass but I have heard that recent advances may have improved upon their usage. I do not believe it would have received an erroneous speed reading being used in this way; however I would suspect the working distance may be reduced and the accuracy of pinpointing the target vehicle may be in question due to refraction of the light if the glass was not 90 deg to the laser.
Hopefully someone with information about laser bending thru a windshield can chime in here.
Do you know if the laser was used thru glass based upon where the LEO was parked and the direction of his vehicle?
I am in British Columbia, I was aware of my surroundings but was focused more on the ending of the passing section and the impending blind curve at the top of the hill. Typically most vehicles accelerate up this section as its fairly steep, and then turns into several long sweeping curves. I do recall a car coming from the other direction around the curve once I crested the hill but I don’t believe it would have been in the line of site of the officer. On the return trip back down the hill I could see why I had missed the location of the police car. He was backed up a temporary driveway hidden behind some bushes with the drivers side window at an angle of approx 45 degrees to the road. I believe the driver was the operator of the laser and would therefore not be pointing through the windshield. I was able to download the operations manual for the Pro-laser III (file is too large to upload here) which informs the operator that:
'Due to the extremely narrow beamwidth of the ProLaser III that makes precise target identification possible, it may be difficult to aim at long ranges if operated handheld.' It also confirms the beamwidth of 3 meters at 1000 meters’ .
Although not relevant i will mention that this province (BC) was the one who spent millions on photo radar equipment, ran it for a while only to cancel the program due to a mass filing of disputes and constitutional legality. Now this guy has a novel approach :)
MSN Autos (EN): Cheeky monkey! Phoenix man uses mask to foil photo radar cameras
I received a phone call from the relevant PD and was informed that the type of laser used was the Ultralite LRV (sounded like a V but could have been a B as it was a voice message)
That would be LRB.
Correct, it was a ULtralyte LR B The specs for this model indicate a Maximum target distance of 1000m so strictly speaking it is within the capabilities of the unit however, i have found case law that limits the distance to 500 FEET Additionally all reccomendations i have sourced thus far recommend use of a tripod or pole for distances over 500 so i will attempt to obtain the training manual or opeartors guide for the ULtralyte LR B to see what it says (unless anyone on here has a copy ?)
Mike and I spoke today on the phone about your particular circumstance and I believe we are of like mind as to what potentially happened, although I won't attempt to speak for him.
It has been my experience with LTI that of all of the police lidar manufacturers (I believe they were the first) that their units possess the highest or most stringent error checking and QoS of any manufacturer.
LTI was the company, I believe, most exposed to the judicial notice process and successfully overcame challenges to their technology many years ago.
As a consequence, I believe the likelihood of an erroneous speed reading is nil.
What Mike and I both believe is a greater possibility is the following:
You pass another vehicle (or two) as you approach an incline and continue to rise in altitude making your vehicle directly visible to the targeting officer (where normally he would not have had a direct line of sight).
The vehicle or vehicles you passed "sped" up to follow up (perhaps at a higher or much higher speed that you were traveling yourself).
The officer (having a line of sight to your vehicle) targets or attempts to target you at this great distance with a lidar beam divergence of nearly 3 metres at that distance.
Your vehicle has a lower lidar cross section than the other vehicle behind you.
A significant amount of the lower portion of the spherical beam strikes one of these other vehicles and a speed reading is obtained off of that vehicle.
Having watched you pass these vehicles, the officer makes the assumption that your vehicle was responsible for the speed reading.
And you are subsequently cited for the violation.
If this sounds plausible to you, as well, I would be inclined to argue the case of these technical points (about the quality of the speed measurement made by the officer).
Given the proximity of the other vehicles and the fact that they may have been extremely close together from the vantage point of the officer, it sounds like a poor targeting scenario with enough question as to whether it should have been even made.
I am pleased that you have found a 500 meter guideline which your officer far exceeded. I am even inclined to reach out to a contact of mine at LTI and get their take on this event as it is not a poor reflection of the the LTI 100LRB (it did its job), but more about how it may have been used in error by the officer.
What do you think?
It sounds like a plausable explanation, in particular as there are two points i have left out, which having researched the subject may be relevant? The vehicle i was driving has a very very low profile, is a two seat convertible (the roof was down at the time) is made of fiberglass and has a diffuser type tinted licence plate cover. The two vehicles i passed were both significantly larger,one being a pick up truck with a canopy.
One other question was raised on another forum so today i parked a vehicle in the exact spot the PC was. It was hidden between two bushes and the officer was shooting between two sections with long foliage. Is it possible that wind movement of the foliage across the face of the beam could have caused an error? ( i will post pictures once it stops raining!) A letter from LTI would be the best case scenario for me as all along i felt it was the distance, coupled with the three vehicles, that resulted in the erroneous reading being recorded. I have researched several laser specification manuals and approx half do state that at distances over half of the max range a tripod or pole type support 'would be helpful'. What do you think the chances are of getting a letter or email from the manufacturer saying something along the lines of when a tripod should be used and what distances should not be exceeded when taking speed reading (i imagine it would be part of the training ? other LTI manuals do state the distances to use)
I doubt that you will receive anything in writing from an LTI or any other Laser company representative as no one is going to go on record with a statement to anyone other than a law enforcement department especially if it contradicts what may have been spelled out in the operators manual, however if there is something in the operators manual, I would suspect that should give you the information you need.
Good luck and keep us posted.
Thanks again Michael, I must confess that this has become something of an obsession now, as an engineer I want to make sense of what I believe was an error. If I am overposting I apologise but I would like to locate the optimum distance (in this I also apologise to Craig, as perhaps I am searching for the answer I want :)) I understand a letter is not realistic but my request would have been along the lines of the factory training guidlines, which may include such information as : 'Do not exceed XXX meters without a tripod or do not exceed XXX with other vehicles within XXX proximity'
I was able to obtain the users manual for the LTI UL LRB (2nd edition 2002) unfortunately it only gives the specifications for min & Max range(Even then its a little vague as it states an 'absolute maximum of ABOUT 1000 meters and can vary dependant upon various factors such as target') and does not indicate an optimal distance or a distance that should not be exceeded hand held (such as can be found in the 20/20 or 100 manuals) I should have saved myself a bunch of time by simply going to the bottom of this page and clicked on similar postings as there is a very informative blog copy from the NMA (sections pasted below)
‘While it’s possible to clock a target that is 2000 to 3000 feet away the speed reading is of dubious accuracy and highly prone to error. On a clear day with no other traffic in sight a good laser operator can obtain reasonably accurate readings out to 1200, perhaps 1500 feet. However, if there are other vehicles present those distances should be halved.’
‘Remember, at distances in excess of 700-800 feet the laser beam is easily large enough to not only be reflecting off of different parts of the target vehicle (which are simultaneously different distances from the laser gun), but also off of other vehicles, some traveling at different speeds. At distances in excess of 800 feet, the laser operator has no way of knowing what vehicle surfaces or entire vehicles are responsible for the laser speed readings, especially if other vehicles fall within the scope of the laser beam.’
‘A vehicle without a front license plate and a low sloping hood, think Corvette, has to be much closer before a good laser reading can be made. However, at distances in excess of 800-900 feet the license plate is indistinguishable from the car as a whole and the laser beam is washing over the entire vehicle.’
‘In an honest courtroom, any laser reading in excess of 800 feet would not be accepted for evidentiary purposes. The State of New Jersey has set the limit at 1000 feet, which is a step in the right direction. The rest of the country is oblivious to the limitations of this technology, with judges and legislators believing the propaganda, instead of exercising the caution and judgment we have entrusted them to exercise on our behalf.’
Day in court
Well the wheels of justice do indeed turn slowly, but after just over a year of originally posting I had my day in court. I would like to say that everything in this post is solely my 'personal opinion' based on my experience with this particular ticket. I researched everything I could find in the year I had to wait and my opinion is that the entire lidar/laser system of ticketing motorists in my province is seriously flawed. Many books on the systems employed are very useful but the bottom line is that Lidar has its limitations and the primary, but not sole, cause of errors is in its incorrect use. I managed to go on a ride along and observed whilst numerous erroneous tickets were issued (980 meters whilst sweeping from left to right through trees, come on!) we played around and managed to get the usual rock traveling at 60 and sweep error is so easy to obtain without error readings I am surprised that anything over 1000 feet is even considered. The New Jersey case law (Judge Stanton ruling) is actually highlighted and forms a part of the powerpoint presentation for the officers training yet its routine to ticket over 2000 feet. Now those with interests in the devices will no doubt heap scorn on the operators however the manufacturers themselves are deliberately vague regarding distance limitations for hand held readings (obviously one persons steady aim is not the same as the guy who has had his 4 double espressos that morning) A look at the UL LRB manual shows little to no mention of beam divergence and I attended over 12 traffic court sessions prior to mine where each and every officer testified (reading from a prepared traffic court checklist) that the device is ‘vehicle specific with a beam width of 0.5 of a meter at 1km’, which is totally false at 3 milliradians. I beat my ticket without too much of a problem because I educated myself about the devices, and whilst I am obviously pleased with the outcome I came away feeling as though I have more questions than answers. Where I live has just introduced the toughest speeding laws in the country, If you are caught travelling at more than 40 KPH over the posted speed limit your vehicle is immediately seized and impounded for one week, and the fine is a minimum of $500. Factor in the towing and impound charges, your taxi home, loss of income, fine and increased insurance and you are looking at a 5 thousand dollar bill. Some would say it’s deserved if you were indeed exceeding the limit by 40 or more, but the way the readings are taken many are not. The law in my province is very clear with regards to the start/end of shift testing accompanied by a test before and after a ticket is issued but in reality this is seldom practiced (even though it is supported by case law) It would appear, in my opinion, that the police and courts are aware that the use of lidar results in a far from flawless reading but that as long as it results in far more convictions than not guilty verdicts then it remains both a deterrent and a revenue generator.
1. Not every State requires officers to be scientific experts on the operation of the Lidar, only the practical operation.
2. You would be hard pressed to find even the cheapest current model lidar painting more than a 3' target at 1000'.
3. A good officer is taking more than one reading and/or tracking the violator vehichle for a long enough to establish a speed.
4. Can't speak for others...but fishing for speeders is good enough that I don't bother with any violators that I'm not 100% on.
5. Not every State cares about distance. Depending on traffic, weather, and road layout, and equipment being used...it is super easy to get people at 1,500-2,000 feet...and easy to get people at 2,500-3,000 feet if you have a magnified scope and steady (rest) the lidar on the edge of your window. That said, I prefer 1,000-1,200 feet for my final reading...but it is nothing to identify people at 2,000 feet, hit them again around 1,500, and then take final readings around the 1,000-1,200 foot mark. It you were speeding at 2,000...speeding at 1,500...and still speeding at 1,200...it is a pretty safe bet that you are speeding :-)
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