GPS Used As Defence In Radar Speeding Case

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."

Video Evidence

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

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

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

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:Video Evidence

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

I don't think so.

Kind of right. What they actually do is reduce the tolerance levels. This happened in Victoria (Australian state - probably has some of the most brutally enforced speeding laws *in the world* - unsurprisingly its roads aren't meaningfully safer), where you will be booked for driving as little as 3km/h over the posted limit (how this lines up with speedometers only having to be accurate within 10% hasn't been tested in court yet AFAIK).

So whereas you use to be able to do 120km/h in a 110 zone without too much to worry about, now you'll get pinged for 114km/h. No-one without an agenda seriously thinks a ~3.6% speed differential has any meaningful impact on road safety.

Police and politicians have to get places by car, too.

Poor examples. Police can (and do) break the speed limit at will with little fear of either detection or punishment. Politicians are typically being driven, for short distances, and only in urban traffic.

Generally I think the speed limits are pretty reasonable. It's just that drivers can't stand any form of restriction, and always want to go faster.

Also untrue. Research has demonstrated that in typical conditions - especially high speed roads like motorways - drivers choose the safest speed for the conditions. People actually interested in road safety know this as the 85th percentile. It's what the posted limit on a road *should* be set at for "maximum safety" (but usually isn't).

For a concrete example, there is a major highway north of Brisbane, Queensland (2 lanes each way, divided, limited access). Some years ago the speed limit was *raised* from 100 to 110km/h (amidst the typical outcries from ignorant fools about how the roads would be awash with blood). Not only does the road remain as safe as it was, but average traffic speed actually *dropped* by about 3km/h.

Seriously, if people can't follow a simple speed limit, why should they be entrusted with more liberty on the road? If people would obey them and drive like sane people, then they could be allowed to drive faster. You have to earn responsibility.

Because following a badly set speed limit - *especially* on higher speed roads like motorways - actually *increases* risk. *DRIVERS* have to earn trust ? What a joke. Maybe if the government was more interested in saving lives than making money - and demonstrated it - we'd be able to trust them with things like speed limits.

Very, *very* few governments have shown any real interest in improving road safety. Why would they ? Doing so would be expensive (both in monetary and political terms) and it's trivial (and cheap) with a good advertising campaign to demonise things like speeding (despite it being a relatively insignificant factor in overall road safety) so they have someone to pin all the "carnage" on.

Re:Video Evidence

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

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

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

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.

Re:Video Evidence

I'm pretty sure that's not what the OP is advocating. If you set up a camera in your car, YOU control it and all the tapes. If you do something illegal or that you don't want taped, you can either turn the camera off beforehand or destroy the tape after. The only place the government comes into this is if you turn the tapes over to the government/court to prove your innocence.

This could only be the first step

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.

Re:This could only be the first step

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.

Re:This could only be the first step

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.

Re:This could only be the first step

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?

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]

used in Taiwan

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.

Brings accuracy into question

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!

Re:Certainly does

Cameras and speed displays don't have radars in them.

They use induction loops buried below the road, and work exactly the same way you do - compare times at positions A and B.

Radar and GPS were in check in California

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.

Testing in UK court case and GPS won

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?

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.

Speed = Distance / Time

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...

Re:Speed = Distance / Time

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:Speed = Distance / Time

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.

Instantaneous velocity

No, my friend, you are wrong.
You see, Instantaneous velocity is the limit of the average velocity where the time of averaging tends to zero.
In other words, the value of f'(t0), where the position x is x = f(t) at a given time t0.
Or in other words, angle of the tangent of the curve x = f(t) in the given time t0.

Now, if your argument is that "a GPS device cannot give the measure of the instantaneous velocity because it does not sample fast enough to get a really good approximation of the curve x = f(t) and hence, the value of f'(t0)", then you could be right because 1Hz is not really a high sampling rate. But you could have said so ;-)

The (analog) speedometer in most cars measure speed by measuring the RPMS of the gear box and multiplying by gear ratios and tire size: they normally do that with a continuous measuring (springs and coils), and what they measure is a good approximation of the instantaneous velocity of the vehicle. A good analog speedometer is somewhat reliable, especially if the scale is correct(*)

(*) their scale is not linear like you see in a normal car:

0 .... 20 .... 40 .... 60 .... 80 .... 100

but exponential, so it should be like:

0 . 20 .. 40 .... 60 ........ 80 .............. 100

and this is why they have a "sweet calibration spot" (normally near the top of the dial; have you already thought about why they make 1.2l-engine cars with 220 km/h marking in the speedometer [a speed they usually don't achieve even in freefall :-)] ?? ) -- in my GM Celta, the sweet spot is at 100 km/h [~60mph], so speeds lower than 100 km/h are usually reading HIGHER than real and speeds higher than 100km/h are usually reading LOWER than real. The speed limit in our highways is 110km/h.

DISCLAIMER: I was a software developer for a road engineering company for one and a half year.

Sorry but you are wrong

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

Punk kid disputes ticket, news at 11!

He has somewhere between 0 and no chance to win this. Who gives a shit what his GPS says. If the radar gun was properly calibrated and can be documented as such, it makes 0 difference - he's screwed.

What's to prevent me from doctoring the GPS log?

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.

GPS more accurate than radar?

I've been sitting in my car PARKED waiting for people and seen my GPS speed go up to 5 mph... I don't see how this can possibly more accurate than a radar gun. a margin error of +/-5 mph seems pretty crappy. (it's a newer Garmin, less than 4 months old.)

I have used this

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.

Re:I have used this

>In San Antonio, TX I was pulled over for doing 76 in a 75 zone.

For what, Driving While Black?

Bah.

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.

speaking of privacy....

The related link tells me that this story was submitted by foxxer [slashdot.org]. But looking at the story and firehose submission (done under a presumably real name and web address), I would never otherwise associate them. But now, anyone that disagrees with one of foxxer's comments knows his name and website.

Strange definition of privacy.

Speeding cases are easy to win

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.

If I were the judge. . .

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, if the judge lets him off this time, it's not as if he's free to do whatever he wants. His parents are punishing him for infractions harsher than the ticket already and likely catching him more often than any speed trap would. This family is a libertarian's dream. I'm not a libertarian, but in this case I think it's easy enough to say "just don't do it again" and trust that this isn't a habitual reckless driver (at least until the next time, if there is one).

Contested speeding ticket

With respect, the issue of the GPS is academic. As a fact, the police officer who recorded the car had retired by the time the case came to court and did not attend as a witness. The prosecution ditched the case as they could not call evidence to say that all correct procedures were followed. The GPS "evidence" may have been the basis of the defence, but the court never had to consider that evidence.

GPS and such.

I use a GPS reciever. Depending the software package I am using I will get various speeds. Normally it is pretty good, but as it has to calculate speed and approximate position based on the data it is recieving. When the unit has road informations it will try to map the data (which is close, but not really close, depending on conditions) to the road. Depending on polling interval changes in direction can have a huge affect (set your interval to 30 seconds or a minute and make a turn or anything that is not linear).

I have a portable unit and software that tracks and logs speed. I do not recall offhand what the polling interval is though. I think at best I can get every few seconds (it may be less--it is average speed and delayed, so it will be how fast I was just going.) If you have a car that can accelerate very quickly try going from a dead stop to high speed as fast as possible. It will not mirror your speedometer. It will follow it. It is taking average speeds after you have begun moving. So when your speed is 30mph it is still calculating using 0+30/time. Fluctuations in speed cause pretty big changes. Again with the vehicle with a transmission designed for quick acceleration: accelerate as quickly as possible to 100mph and then bring the vehicle to a complete stop (disengage ABS if present). The numbers will not be anywhere near the actual speeds. Decrease your polling by 5 seconds and repeat. Do that a few times (it probably is not good for the car.) Better still compare these number with those from RADAR and LIDAR systems.

The gun is only calculating based on really one thing (doppler effect.) Angles and shit can affect numbers, but really it is measuring the speed. The polling interval is still much, much smaller. If it is lidar it could be 1/1000 of a second.

Either way we are looking at an average speed, but the interval during which it is calculated would vary and have a huge effect on the numbers.

This is all before we take into account the security of the data. So, yeah, maybe he did and maybe he did not. But GPS is not as amazing as people think. I guess RADAR is not either. But do not just be hating because you is worried about the man putting you down.

VORAD units have been used this way

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.

Actually, I know 2 ppl who have contested; lost

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.

Ah the memories

This brings back memories, in the late 80's our company was experimenting with GPS. Since at that time there were so few satellites in orbit you had to calculate when you could have 4 in view. This always turned out to be about 3 AM. So there we were cruising down the highways in Western PA at 3AM in a tricked out van full of computers and other things that go beep in the night... Anyway we dreamed of being pulled over by the state cops. "Ok officer let me play that back for you...."

Your Mileage May Vary

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.

GPS used as defence in UK speeding incident

When this went to trial under similar circumstances in the UK, the case was acquited and the fine revoked, even though the media had a frenzy claiming this was due to the GPS data logger -- which the owner likened its accuracy to that of an aircraft's black box (yeah right) -- and the GPS data was submitted as evidence, the case was overturned not due to this, but due to the fact that the prosecuting officer had since left the force and so could not be called upon to persue the case. Otherwise, it would as many have stated, be taking the word of an average citizen over the word of a police constable.

Uups!

This one could strike back..
What if the procecutor asks for _all_ GPS records...
I was playing with a GPS toy and - gosh, did I go _that_ fast? Sure did not want a cop to see those data.
But - luckily, there can be a wide margin of error in a GPS. When it calibrates first, it can be hundreds of feet, even miles off and suddenly, there are speeds of 180 or 300 mph, when it zooms in to higher accuracy. Same can happen, when it looses connection to satellites.

I also have seen whole section of movements, in itself congruent, but offset into another county.

I would argue in that direction - not always reliable and make sure the data are not around long....

SMD vs GPS

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.

WIll he submit the engine computer?

Almost all cars in the last 15 years remember the top speed and rpm you traveled in the past 30 days or so. If he got the ticket on the highway, I would think this second line of evidence might help bolster his case.

I always thought we'd see the reverse

If this guy's case doesn't hold up in court then we'll have a precedent against using GPS to give speeding tickets.

Speed limit wah wah's

I just need to put this out here because I say it every time a speed-limit discussion comes up.

Remember that in most places, speed limits are engineering limits. That means that they must take into consideration any drivers that may appear on the road. That means the random lame-ass 25MPH stretch of country road was labelled that way because it would be unsafe for an 85 year old grandmother with 4 kids in the car, driving an 80,000 pound tractor trailer to go any faster than 25. So, before you claim that the kid in the 4000 lb car couldn't handle it, think about that!

Incline

Wouldn't the GPS only tell your air seed? How would the GPS know if you were traveling at an incline? The Officer's radar gun measures the velocity on the road. The GPS probably compares your coordinates over a short time period and computes your velocity -- hardly accurate if you're traveling at an angle. Unless it's somehow able to factor this in as well. Anyone know?

UK Stuff

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

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.

I work for the radar company...

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.

black box

I would be all for a built in black box in my car that records the last 30 minutes or so of my speed. Of course, just like others have brought up, the cop, knowing it was there by being standard, would probably use it against me.

Already has...

I did this yesterday and failed.... Gem County Vs. Hoye.... Needless to say... Cops analog radar and visual estimate beats multiple satellites. -Bummer for me.

Door swings both ways..

Sure, you can use a GPS to indicate you weren't speeding... but the GPS can also be used to prove guilt in such a violation.

Don't think it sounds so far fetched - I used to work for the local police here. Some of our field services guys would have to drive around in really remote stretches of the country to get to the regional stations. At one station, one of the guys pulls up and walks into the station, where the cops give him a ticket.

The reason? The cops at the station he left radio'd through his departure time. They know exactly how long it takes at the speed limit to get from one station to the next. Our guy had come in significantly under that time. A little time with a calculator and you get his average speed...

Maths... gotta love it!

Re:First Post?

This time, it is the lack of privacy that helps the little guy. Oh, the irony.

Re:admissible?

chain of custody is important for proving guilt (beyond a reasonable doubt). Exculpatory evidence doesn't need such high standards (it just needs to give a judge or jury doubt).

At least in theory. Traffic court judges exist mainly to uphold a cop's decision.

Re:First Post?

Well, it's also filed under "Your Rights Online", however that works.

Re:admissible?

Though I doubt it was done in this case, there is a privacy-maintaining way to prevent tampering after the fact. The GPS could send secure hashes of its data to the GPS vendor, who stores them unmodified and can provide them upon request. Then the car owner can submit the GPS data to the court along with a request for the hash from the GPS vendor. While you cannot recover records from the hash alone, you can verify that they haven't been changed. This does not prevent hacking the GPS beforehand of course, but that is a little bit easier to prove compared to tweaking data.

Re:radar guns are only as reliable as the cop!

Heck here's one idea, put a digital camera inside the radar gun which takes a picture at the same time the speed is detected and print on the receipt, would prove if any other cars were in the vacinity.

In Romania the police does not stop you. Instead the owner gets a nice photo of the car with the speed printed on it, by mail, at home :), together with the speed ticket.

Re:First Post?

I don't get why this is tagged as privacy.

Think about it. This guy is using his GPS data to contest a ticket. Next up, the government subpoena's your car's GPS and/or engine computer info to prove (or snoop on) your whereabouts last Friday night, or to send you tickets based on the readout of your computer (once the wireless interrogation system gets worked out). Do you really want to be under observation at all times and everywhere, regardless of what you may or, most likely, may not have done? I do not.

Re:GPS not even good as a defense against FAA

Depends on the state, bub.

Here in PA, I've fought every single ticket I've ever gotten, because the charge for a real hearing is only like $6.00.

I'd say I end up winning probably 50% of the time. The other half, I get a decent offer (ie, I really was going 30 over, cop offers me 6, i'm gonna take the 2 points).

You just gotta be good at getting the cop to lock up. That is, say they used VASCAR - start throwing math out at him, and explain to him how if he was even a tenth of a second off, it could have been 10 miles an hour slower, etc. Usually, they plain old don't understand you, lock up, and can't respond.

Of course, here in PA, it's just the cop versus you in front of a magistrate. No DA involved unless you appeal the magistrate's decision. The cop never does (however, he may actually have the right to, but good luck finding a local PD that pays well enough for them to actually want to!)