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GPS Used As Defence In Radar Speeding Case 464

Posted by kdawson
from the could-be-onto-something dept.
James Thigpen writes "There is an article over at Ars Technica about an accused speeder contesting his speeding ticket based on his car's built-in GPS system's records. According to the article his car says he was going slower than the radar gun clocked him at. Contesting a ticket based on GPS data has never before been tested in court."
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GPS Used As Defence In Radar Speeding Case

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  • Video Evidence (Score:5, Interesting)

    by ZERO1ZERO (948669) on Saturday October 27, 2007 @02:48PM (#21141623)
    I've often thought it would be a good idea to have a constant video recording your driving, like the police camera setups. This could help clear up who to beleive at the scene of accidents, because of the video.

    Plus it would be cool to have onboard footage of your driving for analysis and review.

    • Re:Video Evidence (Score:5, Insightful)

      by Albert Sandberg (315235) on Saturday October 27, 2007 @02:55PM (#21141699) Homepage
      If you dragrace with yourself and yourself alone one a lone road in the middle of nowhere, does it really matter? I would not like to have the authorities to have a closer look at my driving. I hate the speed cameras they tend to set up everywhere on the road, but in front of schools for instance (where they'd really matter), I'm yet to spot one.
      • Re:Video Evidence (Score:5, Interesting)

        by billcopc (196330) <vrillco@yahoo.com> on Saturday October 27, 2007 @03:26PM (#21141897) Homepage
        Yep, police work is only performed where it matter$, aka speed traps and deliberately low limits. Saving lives is not a profitable business, which is why no matter what you do (or don't do), if a cop shows up, you get a fine.

        In my opinion, if they're not enforcing speed limits in the few areas where they are actually beneficial, then we should abolish that system entirely as it is working for no one. I pay taxes like (most) everyone else, if that money isn't enough to afford proper police without the need for profiteering practices, then raise my goddamned taxes and destroy those stupid radar guns. Maybe then people will start respecting these so-called peace keepers again.

        Something is very very wrong with the world when honest law-abiding citizens live in fear and/or contempt of the law.
        • Re:Video Evidence (Score:4, Interesting)

          by cheater512 (783349) <nick@nickstallman.net> on Saturday October 27, 2007 @08:00PM (#21143993) Homepage
          Sure sometimes radar guns are inaccurate but its also true that people speed and speeding is highly dangerous.

          Imho the latter outweighs the former and radar guns are generally a good thing.
          • Re: (Score:3, Insightful)

            by G-funk (22712)
            Speeding is not dangerous. Driving too fast for your abilities / your car / the road is dangerous, but saying speeding is dangerous is disengenious. That implies that the speed limit has anything to do with safety, which is rediculous. If I drive 80km/hr down a certain patch of road, and one day the speed limit is lowered, I'm not driving any less safely than I was beforehand.

            Speed limits are arbitrary, and (specifically on the highways between Brisbane and Melbourne) designed to make money, not save lives.
            • by dangitman (862676) on Saturday October 27, 2007 @11:06PM (#21144953)

              Speed limits are arbitrary, and (specifically on the highways between Brisbane and Melbourne) designed to make money, not save lives.

              There's a simple solution to that - if you don't exceed the speed limit, they won't make any money from the cameras. So, if they are about making money, then they would be removed once they stopped being profitable. Unfortunately, it seems highly unlikely to get the majority of people to obey the road rules for even one day or one week - so it looks like the cameras are here to stay. I still think it would be a hilarous protest, though - everybody obey the law today, and screw the police and government. It would be an act of civil obedience.

            • Re:Video Evidence (Score:4, Informative)

              by The_Wilschon (782534) on Saturday October 27, 2007 @11:17PM (#21145031) Homepage
              Speed limits are often based on the quality of the road (of the road surface, of the ability of drivers entering the road to see cars coming, and of the ability of drivers on the road to see hazards on the road ahead of them (reduced by curves, for instance)). The road surface quality degrades with time. Occasionally, studies are done in specific areas that demonstrate that the speed limit really is too high for the visibility of the road, both for drivers entering the road and drivers on the road. Other times, the population increases, and thus so does traffic. In each of these situations, reducing the speed limit is the appropriate immediate step. Further steps might include resurfacing the road, widening the road, etc.

              Yes, speed limits are often arbitrary and designed to trap drivers. But claiming that speed limits are never related to safety is foolish, and claiming that speeding is not at all dangerous is also foolish. Higher speed increases both your reaction distance and the severity of any mistakes. Increasing either of these reduces safety.

              I'm glad I don't have to share the road with you.
          • Re:Video Evidence (Score:5, Insightful)

            by KingSkippus (799657) * on Sunday October 28, 2007 @09:03AM (#21147525) Homepage Journal

            Actually, some college students at Georgia State University tried an experiment [google.com] in which they blocked off all lanes on Interstate 285 going 55 miles per hour, the speed limit. Keep in mind that most people drive 65 to 70 on that road.

            As a result, the people behind them got very angry and began active extremely dangerously. One van even had an accident when he passed them on the right shoulder and clipped a car that was parked in the emergency lane.

            There is nothing inherently dangerous about going faster than the speed limit. Sometimes, when it's raining and there is low visibility, driving the speed limit is unsafe. Other times, when there is low traffic volume, high visibility, and the roads are dry, it's perfectly safe to go 10 to 15 miles per hour above the limit. The law doesn't take that into account, though, and as a result, the speed limit is set arbitrarily low on almost every road.

      • Re:Video Evidence (Score:4, Insightful)

        by zippthorne (748122) on Saturday October 27, 2007 @04:14PM (#21142313) Journal
        Problem is, in an age where insurance is a requirement people think that lowering insurance rates is an appropriate goal for public policy. Drag racing, even by yourself on a deserted road, is risky behavior, which raises risk for insurance companies and therefore their rates as well. They're not just going to absorb that loss.
    • Re:Video Evidence (Score:5, Insightful)

      by liquidpele (663430) on Saturday October 27, 2007 @02:55PM (#21141705) Journal
      It would have to be hidden. A lot of cops will make you turn off any recording equipment they see as soon as they start talking to you - and if you don't comply many of them will just arrest you for BS charges. Not saying ALL cops, but I've read articles where already asshole cops went berserk over recording equipment and the person not dropping their pants and bending over to their demands.
    • It might go both ways. If a prosecutor knows that you are recording, they might be able to subpoena it and use it against you.

      The video and data can be used against you as well, they might demand more data than is actually pertinent to the case and nail you for something else instead.
    • by Sparr0 (451780)
      I agree. I have put thought into such a device for a long time. Storage and cameras are small enough now that the entire thing could fit in a 6" hemisphere in the center of the roof of the car (inside). I would want 4 cameras, one facing each direction, with peripheral overlap so that a panorama could be made (with no gaps), plus one camera pointing straight down with a fisheye that covers the areas inside of the car that the other 4 cameras miss. As I envision the device, it would record in a short loo
    • by houghi (78078)
      Yeah, lets help the Homeland Security and give up our privecy without them stealing it. Good plan. After all if you don't do anything wrong, you don't have anything to wory about. Right?[/sarcasm]

      Oh and it can be very cool to analyze how you can NOT kill one of your mates the next time while still driving as fast as possible like in this German movie [dumpalink.com]. Understand this is NOT happening on the german Autobahn, but rather on a 'normal' street.
  • by Kabuthunk (972557) <<moc.liamtoh> <ta> <knuhtubak>> on Saturday October 27, 2007 @02:50PM (#21141651) Homepage
    If this ends up being a valid way to argue against getting a speeding ticket, the next step I see will be people speeding like hell, and then hacking their car's GPS records to show they were going at the speed limit.
    • by kc5goi (772773) on Saturday October 27, 2007 @03:02PM (#21141755) Homepage
      I have heard stories of people trying to submit GPS data logs in the past to prove they were not speeding. The judges would not accept the data because it could be considered suspect, particularly if you presented it on a USB dongle since the data is beyond easy to modify. Radar does have its issues, specifically if you are in a group of cars (have you ever been blamed for speeding when the car beside you was passing you). Unless you can provide data in a method that is deemed "un-crackable", I doubt it would be allowed. I could easily re-run the route that I was on when I got stopped, take the track log and modify the time stamps (if they are present and that depends on the GPS data stream you selected). You would want the time stamps to be there to compare against the time the police officer stated on the ticket. I have to take this jab at the judicial system though, despite the fact the the citations say you are not pleading guilt or innocence at the time of the infraction, you are pretty much labelled guilty, the police never lie in the courts point of view and if you claim you are innocent, you get treated as if you were guilty anyway. The only way I can see to defend yourself is to have the same set up in your car as the police do and have it display speed on the recording. Then again we saw recently what happened someone who tried that in Missouri.
      • by smallfries (601545) on Saturday October 27, 2007 @03:36PM (#21142005) Homepage
        It reminded me of this case [bbc.co.uk] from earlier this month. The inventor in the story was testing his new device when he was clocked by a speed camera. In the court case his GPS logs were used as evidence that he was 12mph slower than the speed gun recorded. He may have had a motive for pursuing it through to a court case as he is starting a company to comercialise the device.
      • I have heard stories of people trying to submit GPS data logs in the past to prove they were not speeding. The judges would not accept the data because it could be considered suspect...
        A GPS unit could be built that fingerprints with a private key, and sealed so that you would just about have to destroy it to hack it.
      • Re: (Score:2, Informative)

        by Anonymous Coward
        This case is special though because this is a kid that had a monitoring system so that his parents could track him. It was designed to not be able to be hacked by someone driving the car. His dad is an ex-sheriff too and has the same story.

        This is an old story by the way. I can't remember when I first read it but it must have been months ago.
      • Completely off topic:

        See, the real problem here is that the people on this site are just to tech savvy. Could you imagine a judge listening to your defense and watching you present GPS data, then sayings "The data you are presenting is not a secure data set and could easily be forged. We therefore cannot accept it as adequate defense. Do you have anything else to say?"

        Of course I couldn't see this happening but it would be a riot.
    • Re: (Score:3, Insightful)

      by j00r0m4nc3r (959816)
      That's exactly why this should not be allowed. Or I could hack my speedometer to always read 25 and keep a video camera in the car. "See, I was only going 25!" People are asshats and will do anything to get out of speeding tickets.

      What I don't understand is how this kid is explaining the discrepancy between his GPS and the radar gun? The radar says he was going 62, but he claims he was going 45? How would that happen? That's a big difference when you consider the accuracy of radar guns. I'm not saying the
      • A lot of things can mess up a radar gun's reading. For example, if the gun was not calibrated recently or calibrated incorrectly. Another issue is the amount of traffic. If the traffic was heavy, then the radar could have easily hit another car that was traveling faster. This is why most tickets have a "Traffic: Light, Medium, Heavy" checkbox section on them. Most officers will default to the light checkbox to help them in court. That's why you bring a camera with you and take pictures of the traffic (assum
    • by c_forq (924234)
      This guys system was so his parents could moniter his speed. Even if you hacked it to report the wrong speed, you still have to deal with how you got between points it reported in the such short between the updates. This isn't your average Garman or Tomtom, this is a system designed for other people to track and monitor the driver.
    • by westlake (615356)
      If this ends up being a valid way to argue against getting a speeding ticket

      There are two big problems with this case:

      1 Malone's parents had the GPS system installed in order to track the whereabouts and speed of their son, whom they readily admit has a lead foot. In fact, he has already been grounded for having gone over 70 MPH after the GPS was installed.

      2 The debate is likely to come down to how often the GPS device calculated and reported ground speed. Petaluma police lieutenant John Edwards told

    • by Paradise Pete (33184) on Saturday October 27, 2007 @05:36PM (#21143013) Journal
      the next step I see will be people speeding like hell, and then hacking their car's GPS records to show they were going at the speed limit.

      Yup. On most people's home projects list that's the one right after "Get microwave to stop blinking 12:00."

  • Open source GPS? (Score:5, Interesting)

    by KillerCow (213458) on Saturday October 27, 2007 @02:53PM (#21141687)
    But will he be able to produce the source code for the GPS when the police request it to check its accuracy?

    Breathalyzer Source Code Revealed [slashdot.org]
    Closed Source -> Charges Dismissed? [slashdot.org]
    • by ls -la (937805)
      I've often wondered if you could demand the source for the radar gun. If it's as bad as the breathalyzer, I'm sure you could easily show there was a good chance it was actually the car passing you at the time.
    • How about the source code of the software on the radar gun? How do we know that works correctly?
    • by JimBobJoe (2758)
      when the police request it to check its accuracy

      Well, it wouldn't be the police who would request the source to check for accuracy, it would be the prosecutors--and that's not a path they would want to go down. They've been fighting it tooth and nail in regards to the breathalysers, and using it against GPS devices would create precedence forcing them to defend the source on every tool police use for traffic enforcement.

  • used in Taiwan (Score:5, Informative)

    by xldyniac (1180595) on Saturday October 27, 2007 @02:56PM (#21141715)
    GPS data was actually used recently in taiwan to prove a man's innocence. A truck driver A went into an accident with a motorcyclist B. A stayed and helped B up, and even paid cash. B said he's fine, so A drove off, only later to recevie a notice that B has filed a hit and run case against him. The court found A not guilty since the gps data showed that A stayed at the site for more than 15 mins.
  • by blhack (921171) * on Saturday October 27, 2007 @02:58PM (#21141733)
    The pretty large difference between his 'radar' speed, and his 'gps'(actual) speed was pretty large. IMHO this sets brings into question just about every speeding ticket ever given by radar gun.....

    lets say that the gun is wrong 1% of the time, which in the case of a cop handing out tickets by hand is okay (imho) because there is human intervention, he (or she) can look at the thing, bang it on his hand a little, and shake the error off as a fluke.
    The speed cameras on the 101 in scottsdale, arizona issue about 250 tickets daily. Thats 2.5 tickets daily that the gun gets wrong (the 1% figure was pulled from my ass, but I'm using it as an example). With THIS there is no human intervention at all (other than a pissed off commuter)..

    grr...not sure where i'm going with this, I just REALLY hate it that humans are being taken out of (at least that little part) of the legal system. I don't want my fate decided by a computer!
  • by CaptainAx (606247) on Saturday October 27, 2007 @03:03PM (#21141761)
    When we were on vacation in CA, we were stopped for speeding on highway 299 and had the GPS running. I told it to stop tracking the rest of the trip so I can get the data later. When I looked at it, it was dead on what the officer clocked us at so I think this person has a good case.
  • by Anonymous Coward
    This was tested in a uk court case and the ticket was cancelled

    http://news.bbc.co.uk/1/hi/england/wear/7033353.stm [bbc.co.uk]
  • Are you serious? (Score:3, Informative)

    by HouseArrest420 (1105077) on Saturday October 27, 2007 @03:07PM (#21141791)

    Contesting a ticket based on GPS data has never before been tested in court."
    Yes it has...read up. The success rate, though, is the same as the rest of the cases. The majority of whom only get off because the cop that pulled them over never show up in court.
  • by imstanny (722685) on Saturday October 27, 2007 @03:08PM (#21141795)
    From my understanding, and the contention of the officer, the GPS logs average speed. Which means that during a short period of time, the defendant could have greatly exceeded the speed limit (and was clocked by the officer at that time), while the average speed was far lower than that. In which case, both the cop and the defendant are correct, and the cop is till valid in giving the ticket...
    • by ls -la (937805) on Saturday October 27, 2007 @03:19PM (#21141857) Journal
      Two things:

      1. What is the time the GPS device averages over? On the devices I've seen it updates about every second. Unless you have a REALLY nice car you're not going to go from 65 to 90 and back down for long enough to average 65 over that kind of time.

      2. At least one state (MA) and perhaps others have laws that require your AVERAGE speed over some distance (I believe MA is 1/4 mi) to be over the limit for a speeding ticket.
      • Re: (Score:3, Funny)

        by vtcodger (957785)
        ***At least one state (MA) and perhaps others have laws that require your AVERAGE speed over some distance (I believe MA is 1/4 mi) to be over the limit for a speeding ticket.***

        They have traffic laws in Massachusetts? When did that happen?

      • 1. What is the time the GPS device averages over? On the devices I've seen it updates about every second. Unless you have a REALLY nice car you're not going to go from 65 to 90 and back down for long enough to average 65 over that kind of time.

        Minor point, but you'd have to go from 40 to 90 in one second then back to 40 the next second to average 65, so you'd need an even nicer car.
    • Many clock max speed. On long hiway trips in unknown areas I keep my eTrex Legend on trip computer with max as a field just in case. I figure a couple dozen DoD satellites might hold sway over a lone radar gun.

    • I have a Garmin GPS mounted on my bike that I use mostly as a speedometer. It has a response time similar to any digital car speedometer I've seen with an accuracy of 0.1 mph. I pass by those stupid "SPEED LIMIT 25 YOUR SPEED: X" signs all the time and the GPS and the sign always agree.
    • Re: (Score:2, Informative)

      by DJGreg (28663)

      First, when the GPS unit itself calculates the speed, it records your instantaneous velocity, not an average. It calculates this using the doppler shift present in the GPS signals picked up by the unit, not from how far the unit has travelled.

      Second, even the cheapest GPS units I've seen update at least once per second.

      Third, the delay, or time offsets of the arrivals of signals from the GPS sattelites are exactly how a GPS unit calculates it's velocity and position. Once a GPS reciever has got a "lock" o

      • by maird (699535)
        I admit I never read the article you provided a link to but just taking what you said at face value I don't believe the doppler effect is used to calculate instantaneous speed. The first obvious factor is that the higher the azimuth of a satellite relative to the receiver the smaller the doppler shift. When a satellite is directly overhead the shift is zero. Therefore, without already knowing your position in three dimensions and the position and instantaneous speed of all satellites you are receiving you c
      • by Paul Jakma (2677) <paul+slashdot@jakma.org> on Saturday October 27, 2007 @05:02PM (#21142713) Homepage Journal
        First, when the GPS unit itself calculates the speed, it records your instantaneous velocity, not an average. It calculates this using the doppler shift present in the GPS signals picked up by the unit, not from how far the unit has travelled.

        Let's go over some basics:

        a) There is no such thing as "instantaneous velocity" - as velocity is a function of time.

        Corrolary: You can /approach/ t=0, but the closer to "near-instantaneous velocity" you try to measure, the more accurate your measurements must be - alternatively the higher the margin of error will be.

        And the problem with the radar/lasar guns is indeed that, because they try calculate "near-instantaneous velocity" they are very *very* susceptible to error, particularly at the ranges the police often try use them at (hundreds of metres).

        b) Noticing a doppler shift in waves from a (relatively) stationary source would require that you have a non-zero velocity relative to the source (ie the distance between you and the source change). I'm reasonably sure this velocity would be immeasurable from a consumer car in a GPS over a short period of time and, further, that any measurable doppler would be due far more to the /satellite/ moving, not the car..

        I.e. I havn't done the calculations (it's not just linear, cause any doppler will be induced by the curvature of the earth, not directly by the car's speed), but you're talking about measuring doppler due to /millimetres/ of movement (curvature of the earth), as a car moves perhaps a tennes of few metres. It's beyond believable we could measure that with any useful accuracy in a car.

        So I call bullshit, unless you show me the numbers to prove otherwise.
        • by Paul Jakma (2677)
          you're talking about measuring doppler due to /millimetres/ of movement (curvature of the earth), as a car moves a tennes of few metres.

          Ah, that's roughly about 1mm for 35m of forward movement btw. For reference, 35ms-1 is about 126km/h (78mph).
      • by laing (303349) on Saturday October 27, 2007 @05:13PM (#21142835)
        GPS units compute your speed by computing the difference between your current position and your previous position divided by the time between samples. There's no other way to do it. Doppler is not involved.

        The time between samples is what's important here. If it's only a few seconds then there's a good case for innocence. If on the other hand it's 30 seconds or a minute, the cop with the radar gun wins. BTW, it is the radar gun that uses doppler to measure speed.

        --
        This space for rent
    • by epine (68316)
      Given the psychology of the driver (young, reckless, and probably resenting his GPS nanny) it is equally plausible that he had figured out exactly how much he could game the system. For every small delay, he would then apply a burst of speed to make up the lost seconds, while maintaining his "average". Given that you have a short sampling window, you need to make up the lost seconds as fast as possible, because you can't necessarily carry them over to the next sampling window.
    • We do not know the sample rate of either the GPS or the radar gun involved. Ooes the GPS data show speed or just distance, and the speed is calculated? If the GPS indicates speed, how is it calculated, based on how many samples? If there is a hill involved, does the GPS show actual ground speed, or projected map speed? If you are going up or down a steep hill, there could be a significant difference between ground speed and projected speed. Clearly the radar gun is measuring ground speed. Without an
    • by tgd (2822)
      When you get down into the shorts of the traffic laws, a lot of states actually define speed limits the same way. In MA, for example, the law states you have to be traveling over the speed limit for a quarter mile -- and a radar reading can't prove that, only pacing can.

      It makes it trivial to get out of speeding tickets in MA, but for some reason people don't seem to know that.
    • Re: (Score:3, Informative)

      by Dun Malg (230075)

      From my understanding, and the contention of the officer, the GPS logs average speed.

      Your understanding and the contention of the officer are correct, but misleading. It's based on a failure to understand how short an interval that average is. GPS units report speed at one second intervals, which is how often the NMEA standard interface updates. Therefore, the speed reading they give is the average speed for that one second interval. This is not meaningful in the context of a 17MPH discrepancy, though, as it's highly doubtful that one could have a large enough swing in velocity over one se

    • by bigpat (158134)

      From my understanding, and the contention of the officer, the GPS logs average speed. Which means that during a short period of time, the defendant could have greatly exceeded the speed limit (and was clocked by the officer at that time), while the average speed was far lower than that. In which case, both the cop and the defendant are correct, and the cop is till valid in giving the ticket...

      and

      The debate is likely to come down to how often the GPS device calculated and reported ground speed. Petaluma police lieutenant John Edwards told the AP that since GPS is satellite-based, there's a delay involved, and that Malone may have sped up and slowed down in the window between measurements, which could be as long as 60 seconds.

      Yes, it comes down to accuracy. But Lieutenant Edwards is wrong about the technology. The GPS satellites do not record the cars movements, so the lag time between the satellite and the car wouldn't matter. The only thing that matters is how often the car's device is recording speed, which could be up to once every second or maybe even more frequently based on the GPS technology alone. Really, what matters here are the technical specifications of the recording device and what data it recorded.

      If it

  • by jordan314 (1052648) on Saturday October 27, 2007 @03:20PM (#21141859)
    On my system the GPS application stores its logs in a textfile which I can easily edit. It would be trivial for me to doctor the text file to contest any speeding ticket. I'm not sure that this is a good form of evidence.
  • I have used this (Score:5, Interesting)

    by www.sorehands.com (142825) on Saturday October 27, 2007 @03:22PM (#21141879) Homepage
    I used the GPS defense when pulled over.

    In San Antonio, TX I was pulled over for doing 76 in a 75 zone. I successfully argued that the GPS was more accurate than the RADAR, when I said that it used "government satellite signals."

    In fact, most police radar units are +/- 3mph. A consumer GPS speed indicator is typically accurate to within .75 mph.

    When working in ship navigation systems (Laser Plot), I was involved in dumping track information from a ship to show that it was not in an area when a boating accident occurred.

    The hacking issue is correct, one can always hack the data. The Cop can lie about the reading on the radar unit too. If it gets to 'real court' you have the standard issues of scientific reliability (Daubert test) and the authenticity of the data. In the late 90s, there was a case (in Georgia, I think) where a speeding conviction was thrown out because there was no reliability of the laser speed testing introduced.

    • by Anonymous Coward on Saturday October 27, 2007 @03:48PM (#21142093)
      >In San Antonio, TX I was pulled over for doing 76 in a 75 zone.

      For what, Driving While Black?
    • by westlake (615356)
      In San Antonio, TX I was pulled over for doing 76 in a 75 zone.

      Assuming that this is not a typo, I am tempted to call BS on this for several reasons.

      Until the repeal of the 55/65 national speed limit, all freeways in the San Antonio area were 55 mph or less, and I-35 was 55 mph all the way to north of New Braunfels. Most freeways inside of Loop 410 have now gone to 60 mph. Outside of 410, speed limits are generally 65 on the Northside and 70 on the Southside. Speed limits jump up to 70 outside of Loop

    • by caluml (551744)
      My home-brew GPS tracker [calum.org] (that runs on my Nokia 95) is very inaccurate. I have to calculate the speed by working out the distance between the lat/lon now, and the lat/lon last time. Bearing in mind I sometimes only get readings +/- 300 metres, it can show me doing 300 mph. And in a wanked old Peugeot diesel, that's not right.
      I'm sure that a dedicated GPS device can devote a lot more chip-space to getting accurate signals though than a phone that does everything.
    • The GPSs that I have used do not triangulate for elevation for their distance and speed calculations, so are usually showing a speed and distance lower than actual. Not sure how that affects the car, but it certainly shows a difference between my bicycle computer and what the GPS says.
    • by jonbryce (703250)
      In Britain, you don't get pulled over unless you are doing > 10% + 2 mph over the speed limit, in a 70 zone - the fastest you will find here, you won't get booked unless you are doing more than 79.
    • Bah. (Score:4, Funny)

      by NotQuiteReal (608241) on Saturday October 27, 2007 @06:58PM (#21143639) Journal
      A consumer GPS speed indicator is typically accurate to within .75 mph.

      So should I get some sort of prize for my Highlander that can go 352 MPH, based on my Garmin 350 "trip max" history?

      I personally don't remember driving 352 MPH, even when driving up I15 to Vegas, but then again, maybe my wife did it when I wasn't in the car with her... yeah that must be it.

  • by Kohath (38547) on Saturday October 27, 2007 @03:26PM (#21141907)
    It's actually supposed to be pretty easy for the defense to win a speeding ticket case. This is true regardless of whether you were actually speeding, GPS data, or any other evidence you present.

    The cops have to prove their case. This means showing up to court with the proper evidence. The evidence has to be maintained and presented in a condition where it is admissible. Very often, one or more of these things do not happen and the defense wins by default.

    Everyone should always take their speeding tickets to court. Speed limit laws need to be made unprofitable for the government and then maybe we can get our freedom back on the roads.
    • by timeOday (582209)
      That's why cops are so eager to ticket people from out of town. Want to contest it? Sure, just show up for your court date here in 3 weeks (chuckle chuckle).
    • Re: (Score:2, Interesting)

      by AgentPaper (968688) *
      Not where I live. Around here, all the cop has to do is show up to win a ticket - ANY ticket, be it for speeding, running a stop sign/light, illegal turn or whatever. Furthermore, regardless of what time the cop is supposed to be in court, the judge/magistrate will usually make you wait till he/she gets there, thereby depriving you of a possible default dismissal.

      I've also been convicted on obviously inadequate or downright forged evidence, as when a cop pulled me over for running a red light and illegal
      • by Kohath (38547)
        That's not a speeding case.

        Speeding cases are different than yours because there's a measurement involved. Even when the cop shows up, he can't say "I saw him going faster than XX speed". No one can be assumed to have the ability to reliably judge speed by sight, and it's easy to demonstrate that. Measurements are only as accurate as a measuring device. The cop has to prove that the radar gun was accurate. These are all hurdles that the cops have to overcome. They fail often.
  • Whether or not the child was speeding, his parents seem to take an active role in policing him. A monetary punishment probably just punishes the parents and the parents have already taken punishment steps in the past. One of the reasons that punishments are as strong as they are is because you're unlikely to be caught every time. This child is more likely to be caught (by his parents) than most and the parents are already grounding the child (which is probably worse than the ticket for a teenager). So,
  • by Animats (122034) on Saturday October 27, 2007 @04:10PM (#21142281) Homepage

    Eaton VORAD units, which are a phased-array anti-collision radar for trucks, have been used to provide evidence in favor of the truck driver. [etrucker.com] The VORAD units track individual car-sized targets, and provide range, range rate, and azimuth. Range and range rate are quite good; azimuth isn't that accurate. The control unit keeps track of recent events ten minutes before a collision, and also has speed info available. The latest versions can interface with GPS and other vehicle systems. This allows detailed accident reconstruction.

    It's most useful where an accident resulted when someone drove in front of a truck. [etrucker.com] The VORAD record shows not just what the VORAD-equipped vehicle was doing, but what the other vehicles were doing.

  • by WindBourne (631190) on Saturday October 27, 2007 @04:11PM (#21142295) Journal
    They had GPS and contested. In Wyoming in one case, and Utah in the other. In both cases, the judge sided with the law. What is needed to prove this is something that is IRREFUTABLE. Right now, the judge assumes that radar is always correct (even when it shows a dead corpse beside a road doing 100 MPH). Want to prove it? Then have a motion camera.
  • by PPH (736903) on Saturday October 27, 2007 @04:40PM (#21142515)
    Don't depend on GPS (or any other) evidence being allowed into court that contradicts the officer's testimony. Some courts may allow GPS data, others may not.


    In most jurisdictions, such traffic cases are considered civil and the standards for evidence are different than those of criminal cases or what you may see on 'Law & Order'. The judge is free to weight the officers evidence more highly than yours and presume it to be correct unless you can show overwhelmingly that it is not. Sort of like being guilty until proven innocent.


    Furthermore, courts have quite a bit of latitude to allow or deny the admissibility of data as evidence. For example: Radar is quite accurate (it reads the speed of an object quite close to its actual speed) but not very selective (it might be reading the speed of something else, or interpret some RF noise as speed). Take the boilerplate testimony that an officer reads about 'calibrating the gun with a tuning fork' and all the b.s. about standards traceability. None of this is necessary, as the most common source of errors are due to poor selectivity. But it sure sounds great in court.


    In fact, calibrating a radar gun with a tuning fork is a good demonstration of its susceptibility to AM noise. An ideal radar gun should only measure frequency shift due to the Doppler effect and reject the sort of modulation that a tuning fork creates. After all, the instantaneous velocity of its tines is dependant on its amplitude and the average velocity is zero (unless you throw it). But no court would hear such an argument, as it would undermine their entire traffic enforcement/revenue collection program. And, as a civil case, they are not required to consider it.

  • SMD vs GPS (Score:4, Informative)

    by RomulusNR (29439) on Saturday October 27, 2007 @06:46PM (#21143547) Homepage
    SMDs measure your speed based on the reflection of light waves traveling straight lines through short distances through clear air. GPS measure your speed by calculating the difference between points derived as the average of the intersection of between 3 and 12 paraboloids determined by light waves traveling through the atmosphere, weather, and possibly reflecting off of buildings, trees, hills, and the ground divided by the update interval.

    Like it or not, the radar gun is a more accurate speed measuring device than a GPS.
  • UK Stuff (Score:3, Informative)

    by mistralol (987952) on Sunday October 28, 2007 @01:26AM (#21145755)

    In the UK the speed camers are checked by hand (or at least are ment to). They do this by taking 2 photos from the camera at a set time interval. On the road by the camera there is meant to be a lot of little white marks which are big enough to see in the camera and are spaced at .25meter lengths apart. So now yo uknow how longits been and how far its traveled the rest is easy :)

    Though i know this system is sometimes ignored by police int he uk ... eg lazy gone home early etc..

    Also in the UK (at least n.ireland) the police are meant to run a test car though speed traps a few times documenting it and keeping a tape etc.. If they fail to produce a copy of the documentation on this to you at the scene if you ask for it then they dont have a case if oyu push it to court.

    Another thought about safty on the road is around where i live they have started putting in speed bumps everywhere. Which is meant to slow the traffic down to improve safty. Slow it donw it does. It also annoys the crap out of people driving over bumps all the time and it makes the safty problem worse. Since all the traffic is now slower no gaps form in it so people can no longer cross the road when its busy whichout taking higher risks which is exactly the opposite they were traying to prevent.

    Its amazing what the UK goverment can come up with.

  • Not Going To Work (Score:5, Informative)

    by Anonymous Coward on Sunday October 28, 2007 @01:36AM (#21145793)
    It's probably far too late to get a mod up on this, but I thought I'd add it to the knowledge base of the Internet in case somebody decides to Google it one day.

    Simply put: This is not going to work.

    The system is rigged against fighting speeding tickets. Even if you've got the money to pay for evidence collection, expert witnesses, and everything else -- BEFORE your trial -- you'll still lose. The justice system will protect the police from having even one ticket investigated, because it calls into question other tickets the officer may have written using the same or similar equipment; a very large expense. It just won't happen.

    Here's a TRUE story, as related to me by my friend who drives commercial truck:

    My friend was pulled over by a police officer for "speeding" and given a ticket for 75 in a 65. Only one small problem here: The area in Ohio where he received the ticket was absolutely flat, and his truck is GOVERNED at 68. Exceeding 68 miles per hour on a flat road is literally IMPOSSIBLE for his truck, so says the manufacturer of the engine and the manufacturer of the vehicle. Understandably, my friend was very upset at receiving such an obviously bogus ticket, and decided to fight it.

    Nice thing for my friend, engines in big trucks have computers to track fuel usage, speed, etc. over time. Getting the data from the engine is a matter of taking it to the service center, hooking up a computer, and getting a printout. He obtained this printout and showed it to me; it's so simple my grandmother could easily see his truck hadn't gone over 68 at any point during the data recording. The dates were clearly marked; it showed on the day in question, the truck did not go anywhere near 75.

    Armed with this and people willing to testify that the truck's governor was functional and the printout was accurate, he attempted to fight the ticket. He was informed that he would have to pay all of the trial costs up front ($10,000) before the trial began, and even if he won, he wouldn't be able to get reimbursed for this expense. So basically, it came down to a choice: Swallow pride and pay the $350 ticket, or pay $10,000 to prove he was in the right and get the ticket voided on the basis of the evidence.

    Sadly, but wisely, my friend opted for the former. Proving his case was not worth the extra $9650 it would cost to do so.

    Take note: Traffic court is rigged against regular people. If the highwaymen in blue try to rob you, just give up the money; losing your time, energy, and sanity over government sponsored theft will just victimize you more.
  • by crazybilly (947714) on Sunday October 28, 2007 @02:24AM (#21146049) Homepage Journal

    I work for the radar company that made the radar gun the cop used. I don't have all the information about what happened, but I have a hard time believing the GPS is more accurate.

    Radar guns are certified regularly, which is most often a pretty simple accuracy test (but very well could have been a full diagnostic), so it's doubtful the radar gun was malfunctioning (iirc, those guns have an internal lockout in case of malfunction).

    Also, remember that we're talking basically the speed of light here, with some minor latency for the unit to process the Doppler shift. Radar's pretty much instaneous, within miliseconds, at least.

    Now, that's not to say that the officer didn't make an error. Radar's not an exact tool--b/c the beam is so wide, you can pick up a lot of things and an untrained officer can get some misleading speeds.

    At the same time, remember that most traffic officers do this all day, at least five days a week. They make mistakes just like anybody else, but they're rare. And for that matter, officers are trained to use the radar as a confirmation of their own judgement of how fast the vehicle's moving. And since they're doing it all day long every day, they can tell you within a mph or two how fast a car is going just by looking at it.

    Again, I'm not pretending to have all the information, but if it came down to trusting GPS or trusting the radar, I'd trust the radar. It's just a simpler tool, with less hoops to jump through (and fewer things to go wrong).

    Disclaimer: I'm in marketing for Decatur Electronics [decaturradar.com]. But for what it's worth, I use Linux on my machine at home, hehehe.

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