Guy Uses GPS Data On Mobile Phone To Get Out Of A Speeding Ticket

from the now-that's-how-it's-done dept

We’ve heard a few stories here and there of people trying to use GPS data to get out of speeding tickets, and apparently in some cases it’s working. A guy who was running some tracking software on his Android smartphone realized well after he received a speeding ticket that the phone had actually been tracking his speed and showed he was not, in fact, violating the speed limit. When it came time to protest the ticket, the judge was a bit skeptical, but the guy had a lot of info backing him up:

I then presented my time stamped GPS data with details about my average moving speed and maximum speed during my short drive home. Both numbers were well within the posted speed limits.

I also made it clear to the judge that I had no other prior driving records or violations. After a lengthy pause, the judge asked how I obtained the GPS tracking information. I provided a detailed explanation about my new awesome smart phone, the application in use, and how I exported the data. After questioning whether the data was reliable, I mentioned the in progress Sonoma County Superior Court trial regarding the same matter about the credibility of both technologies.

The judge found him not guilty but was careful not to include his GPS phone information in the judgement.

Perhaps it’s time to start tracking my driving habits on my phone…

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Comments on “Guy Uses GPS Data On Mobile Phone To Get Out Of A Speeding Ticket”

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Rabbit80 says:

Speeding tickets should only be issued if there is at least 2 photographs taken at a fixed time apart with distance markers on the road as well. Without these there is no way of knowing if the speed indicated on the gun is accurate. A shaky hand, a gust of wind etc can all skew the results from a radar gun – I’ve even seen radar guns record brick walls doing over 100mph!

Chronno S. Trigger (profile) says:

I'd suggest

I was just about to ask what app that was (specifically I was going to say “is there an app for that”). I have that installed, I just haven’t played with it yet. I guess I will have to now.

I have found that my old GPS is much more accurate then the speed signs on the side of the road or even my speedometer in my car (though, this is the US, all cars are like that).

Overcast (profile) says:

“Perhaps it’s time to start tracking my driving habits on my phone… “

Indeed, that almost makes me want to get a smartphone.

Of course, you know it’s not long off – that this will be used in reverse..

They’ll complain they don’t have the funds to keep police working on traffic all the time. GPS will automate the speeding ticket writing process.

CharlieM (profile) says:

Sorry, previous post didn’t post completely…

For a long time now I had wanted some sort of “Software” package suit for my car. Something like a “Black Box” – perhaps recording speed, direction, location, GPS, ect., and hell, even a camera or two in front and behind me stored on the black box.

All started when I got blamed for hitting a car that ran a red (lady was banging a cop… written up entirely my fault)

Obviously, anyone as paranoid about liability as I am, is certainly as paranoid about privacy, and would only want this info to be ‘legally’ usable by me (its my black box).

Maybe its too expensive? not enough demand (yet)? Stupid idea? What you think?

Damon says:

People considering running GPS tracking apps while driving or all the time should know it drains the battery fast. My android phone will be dead after tracking for 8-9 hours, but lasts around 40-50 without the GPS.

Cars don’t need GPS to record speed, the on-board computer of all cars since the 90’s provides all kinds of things like speed, pedal positions, fuel use, etc. I’m not sure that it logs it, but with an OBD2 adapter, you can record it on a pc or data logger This is instant speed as measured from the wheels. GPS uses average speed. I’m surprised GPS would be deemed legal in defense of a speeding ticket, because you could obviously speed for a short time without averaging over the limit. Additionally GPS is designed to give position, which it does very well. Other derived data, like speed and elevation are no where near as accurate.

Gwiz (profile) says:

I can see it now

Once every car is equipped with built-in GPS, governments will make it a law that all logs be searchable for traffic violations.

Once every car is equipped with built-in GPS I will most definitely be disabling or removing it from my car whether there is law against it or not. As it is now, I refuse to own a car with OnStar or equivalent for that exact reason.

Rabbit80 says:


The cars internal sensors cannot be relied upon – even the ones that read the wheel speed directly. Seemingly small changes to the wheels diameter caused by tyre pressures, temperature and tread wear can make quite a difference to the circumference of the wheel – which is what is needed to accurately measure the vehicles speed.

GPS on the other hand uses the speed=distance/time formula which is extremely accurate. GPS units generally refresh a couple of times per second so the average speed you see is pretty accurate unless accelerating or braking extremely hard – this would be obvious by looking at the speed results either side of the reading.

Christopher (profile) says:

This won't work as-is.

The judge disallowed the GPS results because there was no certification of the data. I can create a GPX file with a text editor; does that meet the test of certification?

No, you need to prove that the results could only have occurred on that device, at the time contained in the data, and the log was unaltered; furthermore, you would need to demonstrate the either the log could not be altered or the alteration is always detectable. In other words, a sealed black box that has been quality-tested and validated.

Eight years of pharma validation experience backs me up. Your device doesn’t meet 21 CFR Part 11.


coldbrew says:


I’m sure many of us have conceived of a HW/SW solution to handle the question, “Who will watch the watchmen?”

Businesses do it to manage risk currently, and eventually this tech is commoditized and brought to consumers. Trucking companies have been using tech similar to that in this post for a decade.

You could be first to market ๐Ÿ™‚

TheStupidOne says:


“Obviously, anyone as paranoid about liability as I am, is certainly as paranoid about privacy, and would only want this info to be ‘legally’ usable by me (its my black box).”

Unfortunately that won’t happen. If you have this sort of data and you are sued or are accused of committing a crime for something done in your car, then your black box will become evidence regardless of what you want.

Beta (profile) says:

This won't work as-is.

Cryptographic timestamps can prove that a log existed at a certain time and has not been altered since. The tricky part is proving that the log was not complete fiction when it was created.

How about a web-of-trust approach: imagine an app that allows two mobile devices to talk to each other and measure their separation distance (or at least put bounds on it). As you travel, your device shakes hands with other devices (pseudonymously), leaving a kind of alibi trail. If and when you’re stopped by the police, you ask that your device’s serial number be recorded in evidence, or better still, that it shake hands with police devices. Then in court you unmask the pseudonym and put out a call on the web for others (“e-witnesses”? sorry) to reveal their handshake records, along with third-party stamps. If you want to fake your travel history, you’ll need a lot of accomplices.

Danny (user link) says:

Wait for it...

Give it about a year before law makers start pushing to have things like GPS data excluded from such cases. Well only that citizens won’t be allowed to. Rest assured if a cop has GPS data showing you are speeding that will still be allowed and if you’re big company you will be allowed to do so as well. Can’t have GPS getting in the way of corporate and law enforcement bullying can we?

btr1701 (profile) says:


> Obviously, anyone as paranoid about
> liability as I am, is certainly as
> paranoid about privacy, and would only
> want this info to be ‘legally’ usable by
> me (its my black box).

Doesn’t matter whether it’s your box or not. It would still be discoverable subject to subpoena in a civil or criminal trial. If you hit another lady in an intersection and she sues you, you better keep that black box a secret because if the plaintiff finds out about it, the judge will order you to produce it and its records for examination.

papapump (profile) says:

Officer Discretion

I really think all speeding cases should come down to officer discretion. Granted, we’d have to rely on the officers’ morals and judgement, but I really feel like this is the only way to keep our privacy and maintain order on the streets. Most people drive reasonably voluntarily, and most officers are not out to fuck over the average Joe.

Any time I’ve been pulled over for speeding in California, the officers have stated they estimated my speed at “such-and-such” and the radar indicated “so-and-so.” I believe they do this as a layer of evidence in case the validity of the radar is challenged.

I would prefer if driving infractions were treated on a case-by-case basis. I feel that in this case, we would do without traffic cams and radar guns, and rather just have the officers give tickets to drivers that may actually be driving dangerously. Currently, I live in Oregon, where the speed “limit” is posted at 55 mph on most highways. I’ve been told that that speed is posted as more of a suggestion, and can verify that so far, going 69 mph has been perfectly acceptable to the state troopers I’ve passed. It makes a lot more sense this way as I can safely drive much faster than 55 mph in the high desert, though I can’t say that a tractor-trailer in the snow is safe at that speed.

Officers already have discretion in this area when it comes to weather conditions, and I feel most of them are trained to make an okay judgement here. Do away with speed limits altogether and stop using police as revenue generators.

Derek Kerton (profile) says:


“Having a GPS is for all intent and purposes like having an atomic-clock with you.”

True, but a highly precise clock, by itself, does not produce extremely accurate speed calculations — that also requires extremely accurate knowledge of two successive positions. I would trust a radar gun over a GPS every time.

Why? The problem is that the GPS calculates speed based on the time it takes for you to travel between two recently calculated locations. It does this many times a second.

However, how accurate is your GPS? At best, it is probably +- 1 meter. Over the course of a long trip (a mile or more), it will do a very good job of calculating average speed. However, for a very short trip, say a few meters, it may use two specific position fixes that are both wrong by 1+ meters.

If you are traveling due east, and the start fix is wrong by 1 meter west, and the end fix is wrong by 1 meter east, then the distance traveled will be over-estimated. The speed for that trip will, thus, be over-estimated. This will, in turn, provide an incorrect maximum speed.

Derek Kerton (profile) says:


“speed=distance/time formula which is extremely accurate.”

The formula is accurate, but is the input data?

GPS normally offer position fixes that are wrong by 3 to 15 meters. If you are taking speed measurements many times a second, as you correctly say, then the distances traveled would be less than 27 meters at freeway speed (100km/h).

Would you really argue that using two position fixes with accuracy of +-3 meters over a distance of

Derek Kerton (profile) says:


…f’n code tags!

…Would you really argue that using two position fixes with accuracy of +-3 meters over a distance of less than 27 meters would produce an accurate estimate of distance traveled?

While the formula, s=d/t, may be accurate, it is vulnerable to the rules of garbage in, garbage out. Basically, GPSs suck at calculating instantaneous velocity. A simple example some might have observed would be when you are stationary, and your GPS velocity arrow keeps indicating movement in random directions, and the GPS reports intermittent motion of a few mph.

In practice, GPSs appear to do a pretty good job, by using longer intervals to correct for or mask errors (this just depends on the software). But they are still not as accurate as a properly used radar gun, or even a properly calibrated speedometer.

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