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  1. #1
    sledge2k2 is offline Junior Member sledge2k2 is on a distinguished road
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    Question Can Lidar be used in rain/sleet/windshield?

    Hello! My brother was recently pulled over for speeding at 14mph over the post 65 MPH speed limit. I was in the passenger seat and saw the police car ahead on a wide shoulder. perpendicular to the road. I mentioned the fact to my brother and he said "we are only going 72" he thought nothing of it. Sure enough, the cop pulled us over. Supposedly he used Laser from 550 ft, but some things dont line up.

    I saw the police car, plain as day. The officer was just sitting there in the car with the window closed, not standing outside or pointing the gun out the window or anything like I have seen others do. To my knowledge, glass reflacts light, including laser so I dont understand how this could work accurately.

    Also, can lidar be used in sleeting conditions? From my experience, snow, sleet, rain, etc all reflect/refract light. It was sleeting outside with a surface relative humidity of 97% all of that morning, and all of the local airport METARs reported this as well (Im a pilot :cool: ).

    My question to you (hopefully police officers) is that are these devices reliable under these conditions? If they are not, I would like to believe the Officer knew about these limitations of laser so I dont understand why he would use the device under such conditions. :confused:

    Thanks for any info you guys might know about this.

  2. #2
    DepDog's Avatar
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    The laser is extremely reliable. I am a certified laser operator and use the device everyday. You can use the laser to shoot through a window, although the range is limited, but at 550 feet it will work.

    Yes the device will work in rain, sleet or snow, again the range is limited because the laser beam does refract off windows, rain, sleet and snow but you can accuratley obtain speed readings. But I dont use the laser in the rain because I dont like getting wet

    If you and your brother dont feel you were speeding request a hearing.

  3. #3
    sledge2k2 is offline Junior Member sledge2k2 is on a distinguished road
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    Depdog, thanks for the response! To some extent, it is a relief that it seems it was used properly. Of course we are still at a loss as to why he got the reading he did. I mean, true he was speeding +7 but you can literally get run off the road doing 65mph on I94, even though it is the speed limit. Personally I am usually doing 70 in the right lane and I still feel like a roadblock! :cool:

    From the looks of it, he's going to attempt to plea it down to the lower speed violation, since he was speeding after all, just not as fast as was claimed. Hopefully the CA will be reasonable about it. If not, lidar has no judicial notice here so I suppose he could drag the CA through the mud to get an expert witness if he really had to. Kind of a cheap shot though in my opinion.

    That brings up an interesting topic actually. I am surprised with Lidar being used for what, a decade (maybe more?) that more jurisdictions are getting it on judicial notice. It's beneficial for everybody because it prevents the prosecution from having to waste time and money with expert witnesses, and it lays down guidelines for it to be used as evidence. That way, so long as the judicial notice's requirements are met, the evidence is admissible and incontestible.

  4. #4
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    Just some added infor on LIDAR, I use the Pro Laser III by Kustom and it has a bad weather setting to shoot through sleet, rain , snow and fog. You can shoot through glass, however it is harder to do, and I usually roll down my window. The range of the Pro Laser III is between 4,000 to 5,000 feet, and for every thousand feet the beam is three feet high by three feet wide. Never be contested in my state, and as of the three years I have been using it, have never found it to make an error. Either it works or it don't.

  5. #5
    ua8898 is offline Junior Member ua8898 is on a distinguished road
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    How difficult is it to pick out a vehicle at 1000', 2000' in moderate traffic? Is it very difficult to single out a vehicle or hold the unit steady enough to aim at a car that far away?

  6. #6
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    :rolleyes: Get your speedometer calibrated and stop watching too much TV.

    "ching ching, pull it over buddy. You're under arrest...get in the basket." ~ Super Six 5

  7. #7
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    scott715us is offline Sgt/DUI Inst/Juris Doctor scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute scott715us has a reputation beyond repute
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    Quote Originally Posted by ua8898
    How difficult is it to pick out a vehicle at 1000', 2000' in moderate traffic? Is it very difficult to single out a vehicle or hold the unit steady enough to aim at a car that far away?

    Ever played laser tag? All you do (for the Pro Laser series) is place the red dot on the car and that's the car you lock. Not hard at all. Most of the Pro Laser series come with shoulder mounts if you need to use them. They are accurate and very rarely contested. Our judges do not like people who try and contest any radar. Most of the folks, even if they say they were not going the speed the officer stated, still incriminate themselves by stating they were going "60 in a 50 instead of 64 or 70." Alot don't realize 1 mph over is speeding. Pretty funny. ;)

  8. #8
    txinvestigator1's Avatar
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    And glass does not reflect much light at all, it passes through. It would be impossible to see from a window if glass reflected light. ;)
    "Speed is fine, but accuracy is final" --Bill Jordan

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  9. #9
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    Glass doesn't reflect light as much as it REFRACTS it. Remember the glass prism with the rainbow? That works by shooting a ray of light through one angled side and seeing the seven different wavelengths of light at there different frequencies refract. The greater the angle of the ray entering the glass, the greater the level of refraction, hence the index of refraction. Basically, YES lasers will work on glass in the same way that light does, but can still have a small margin of error due to refraction. That is almost incalculabel to any relavent degree. Sorry for the rambling...hope that helped some.

    P.S. I WAS a physics major specializing in light and optics before choosing my present career path.
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