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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."
I don't get why this is tagged as privacy.
Dance Dance Revolution.
Plus it would be cool to have onboard footage of your driving for analysis and review.
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.
Planet Zebeth - Metroid with a twist
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
Closed Source -> Charges Dismissed?
How is the 'chain of custody' maintained here? Can the data be admissible due to the opportunity for tampering?
You could show any speed in the data.
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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.
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!
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if true, very relevant.
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.
This was tested in a uk court case and the ticket was cancelled
http://news.bbc.co.uk/1/hi/england/wear/7033353.stm
This is Slashdot! Give me the latest gadget, bug, or OS project! This ain't english class so don't confuse the two!
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...
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.
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'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.)
sigs... don't talk to me about sigs....
I used the GPS defense when pulled over.
.75 mph.
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
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.
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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.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
The related link tells me that this story was submitted by foxxer. 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.
Do you even lift?
These aren't the 'roids you're looking for.
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.
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).
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.
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 answers to these questions, it's all just speculation.
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.
I meant El Paso. I don't know why I typed San Antonio.
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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. 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. The VORAD record shows not just what the VORAD-equipped vehicle was doing, but what the other vehicles were doing.
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.
I prefer the "u" in honour as it seems to be missing these days.
print it, everyone believes a hard copy
I had a friend who was stopped for speeding recently, doing 42 in a 35. He knew he was not sppeding, after looking at the ticket decided to contest in court, the cop make 3 mistakes on the ticket (wrong color of car, street name incorrect, whether driver was owner or just operator) plus the cop said that there was a posted 35mph sign and that a judge lived nearby so he is on the street a lot.
He went to court for a preliminary hearing, and the judge said that he knows the fore-mentioned judge who lived on the street and there is indeed a posted 35mph sign. He made another court appointment for a few weeks later.
My friend went and recorded the street in the direction he had travelled with a digital camera to prove there was no sign, which there was not.
When in court my friend put forward the reasonable doubt that how in all good faith could he believe the cop's reading of the radar when the cop was incapable of copying down the car's color (clearly printed on the reg) and writing the other incorrect details on the ticket. When the cop argued that it is indeed a posted 35mph zone, my friend produced the video footage, the judge viewed and threw the case out saying that he had presented more than enough reasonable doubt.
Magically the next day, a new 35mph sign was installed on the street, which my friend saw being installed by two city workers.
And this begs a bigger question... How do we know as citizens that when we are stopped for speeding the cop isn't showing a speed from a previous stop or from a car passing along etc... Perhaps speed guns should print receipts (like voting machine should!!!) which tell you offier id, radar gun id, certification number (don't radar guns have to be calibrated from time to time), date/time, speed etc...
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.
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...."
Round here there's a lot of those radars which show your speed, and a smiley or frowny face. They all read 5 to 10% high, compared to GPS.
I've been photographed several times by automatic speed traps, and each time my GPS log has shown that I've been driving under the speed limit. I trust the GPS, because I can see that it reads the time and position correctly. Thus I can work out my speed by hand, and compare it to the speed shown by the GPS.
So far no speeding tickets have arrived in the post. Maybe in the speed-camera pictures they can see me with my GPS, pocket calculator, pencil and notepad. And maybe they think, "there goes a safe driver".
... Public Space mean anything to you?
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.
Have gnu, will travel.
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
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.
Simply because the prosecution will obtain technical data from the GPS manufacturer detailing the accuracy of the GPS itself. Even Military GPS systems are only accurate within a certain distance, so public GPS systems will be even less "accurate"....so, once they show the variance, the GPS data could show that the person "could" have been going slower..."could" have been going faster, or anything else inbetween.
This is one of the most emblematic cases for justice, since GPS is a technology from the NASA and the speedometers are military technology. Such abiguity should never happen, but it is real. There are scientific and observational data, and there IS REAL SCIENTIFIC DATA without any human (police) intervention.-
See you in court, mf.
?
>>> "Unless you can provide data in a method that is deemed "un-crackable", I doubt it would be allowed."
Sure people would be suspicious but the burden of proof lies with those that have to show your evidence is not valid, surely - presumption of innocence and all. Either they show you fabricated the evidence (and are thus due an even longer stretch in prison) or they don't and your evidence stands. Indeed if your evidence doesn't balance with that of the police then there's something for the jurors to weigh against you.
However I suspect the tolerances of the GPS speed and police speed systems are such that you could have sped but appeared to be within the police tolerance zone (about 10% I think).
That is: you do 77mph in a 70mph. Except tolerance of your GPS is 5% so you're actually doing 80mph. Error band of police equipment is say 2% (when used correctly). You're booked as they are sure you're going over the limit and know it.
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....
GPS receivers use Doppler to track the signal being received from the SVs; but that is the Doppler from the relative velocity between each of the SVs and the GPS receiver.
(I used to work on a military GPS system.)
The accuracy is based on the specifications of the unit.
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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.
Terrorists can attack freedom, but only Congress can destroy it.
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.
This issue is a bit more complicated than you think.
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: but exponential, so it should be like: 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
DISCLAIMER: I was a software developer for a road engineering company for one and a half year.
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
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 love my system system.
Hire 100 college students that live some place more or less flat and treeless, preferably from small towns so there aren't "skyscrapers" to contend with, to drive around with GPS for some length of time. After the time has elapsed, look at the data for contiguous data points that have an anomalously low variance in speed prediction. Publish the best set of data you can find as the specs for the instrument.
Sorry, unless you are doing local differential corrections, you are not going to get high precision out of GPS derived speed measurements. Or, perhaps you are using military grade GPS? Civilian data just isn't that accurate.
If this guy's case doesn't hold up in court then we'll have a precedent against using GPS to give speeding tickets.
God spoke to me.
The FAA will issue FAR violations based on single-point radar data that can be inaccurate on the order of miles in any direction. Violated pilots often attempt to use GPS data, which is hyperaccurate in comparison, but usually don't get anywhere with it.
Bottom line is, traffic courts are just kangaroo courts - revenue generating machines for local and state governments. Traffic judges are not interested in justice. They are interested in generating revenue. Facts and circumstances are irrelevant.
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!
I'm not sure about other states, but in California there is no subpoena process for infractions. There is discovery, where you can demand a list of witnesses and copies of all documents/data to be used as evidence against you. The people would have no access to your GPS records unless you intend to use them in your defense.
Also, In most cases there is no prosecutor (the DA is too busy fighting real crime,) so there is no discovery against you.
GPS receivers typically calculate velocity by measuring the frequency shift (Doppler shift) of the GPS D-band carrier(s). Velocity accuracy can be scenario dependent, (multipath, obstructed sky view from the dash of a car, mountains, city canyons, bad DOP) but 0.2 m/sec per axis (95%) is achievable for PPS and SPS velocity accuracy is the same as PPS when SA is off.
Velocity measured by a GPS is inherently 3 dimension, but consumer GPS receivers only report 2D (horizontal) speed on their readout. Garmin's specifications quote 0.1mph accuracy but due to signal degredation problems noted above, perhaps 0.5mph accuracy in typical automobile applications would be what you can count on. Now, they may average the readings over a period of time to give better smoothing etc.
Ever stop to think
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?
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
Though i know this system is sometimes ignored by police int he uk
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.
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 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. But for what it's worth, I use Linux on my machine at home, hehehe.
It seems to me that what stops you from doctoring the logs is the same thing that stops the police officer from falsely testifying as to the readout of the radar gun.
It's next to impossible to modify the Active Log track data on a Garmin GPS devices. That's the log file the GPS stores the current track data (usually the last 10,000 points) and it can only be downloaded to the computer. It can not be uploaded back. Any tracks that are uploaded from your computer are clearly marked. You could possibly disassemble the device and reprogram the chip but it would have to be done on the spot in a few seconds after being pulled over which is completely impossible. I can see absolutely no way you can fake the Garmin GPS data if you present the device as evidence on the spot. Also, from my experience, GPS devices are pretty accurate on the open road (much more accurate that the speed indicator in your car). And if the recorded speed is not correct it is always easily identified from an obvious positional error (if the positional data is more or less correct, so is the speed data).
Never mind that half of that road is closed for repairs and some repair worker might be brushed as you rip through the patch.
It could also be that the road developed some new bumps or that yesterday a new school has been opened besides it.
There are many reasons (besides money harvesting) that would warrant a new speed limit.
Patents Drive Free Software as Hurricanes Drive Construction Industry
even if everyone obeyed the laws it wouldn't matter. as a recent episode of Inside Edition revealed police have to make a quota of busts as a performance standard (and no negative points for busting innocent people if there aren't enough violators around). so if everyone obeyed the law at your camera thing they would probably just rig the machine to randomly pick people and falsify their speed.
The law in MA states that if no speed limit sign is posted the average speed of a distance is:
30 MPH for 1/8 mile in a "thickly settled" area (business district, or where houses average less than 200 feet apart for 1/4 mile).
40 MPH for 1/4 mile on an undivided highway outside a thickly settled area.
50 MPH for 1/4 mile on a divided highway outside a thickly settled area.
20 MPH in a school zone.
However, there are lots of speed limit signs in Massachusetts, so this law is rarely necessary. Furthermore, although the law makes that evidence prima facie, you are allowed to present evidence that the speed you were going in excess of those standards was reasonable [sunny day, open road, etc]. I have no idea if pointing out that the radar gun was used -- and therefore wasn't a measurement over a long enough distance -- has ever been tried.
Support a few technologists in Washington.
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.
Thank god I don't have a piece of crap like that. My bargain SIRF-based gps receiver updates every second, and I have never seen it jump positions by 500 feet in a single tick once it was locked(which would be about 350MPH or so). You need better equipment.
The unit I've got, a bluetooth one that connect with my phone, is mounted in the glasses case of my F150, right next to the steel cab hood, and in zero unobstructed view of the sky. I get, typically, 7-8 satellites at about 50-80% strength. If I put it on the dash, I get an extra 1-3 birds, with signals improved by 10-20% across the board. Either your equipment sucks balls, or something's wrong with it.
Is it just my observation, or are there way too many stupid people in the world?
...DISCLAIMER: I was a software developer for a road engineering company for one and a half year.
But you're still not an engineer, obviously. If you were you'd know:
The real-world is chaotic, both inherent in the systems found there, and in how we can measure them. They do not quite conform to the nice, precise graph on your screen, no matter how clever your math. It's extremely important, as an engineer dealing with physical systems at least, to know to model and then account for error. Actually, as I developed the software (and hardware) that engineers used to measure and calculate all the approximations of things -- yes, I didn't write administrative software, but engineering software (*) --, I am fully aware of that! That's why I said if you wanted to say "we can't measure appropriately instantaneous velocity", that is what you should have said, and not "there is no such thing as instantaneous velocity". They are actually different.
(*) specifically, and amongst other stuff, software and hardware to measure and tabulate pavement irregularities and optimize deployment of resources to fix them.
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
damn, i noticed those that say "i'm going to be modded down for this, but...." usually avoid getting modded down, or even get modded up. i guess that's not the case here. my, this field i'm typing into has the perfect dimensions!
My, slashdot, this field I'm typing into has the perfect dimensions!
http://youtube.com/watch?v=XwsR3XmkCCg
They do NOT use aprons 100% of the time. Know what you are talking about before you post, okay?
Another issue is how GPS calculates your speed. It does not do this the same as a radar gun. A radar gun takes an instantaneous measurement of your velocity. GPS calculates your AVERAGE velocity from adjoining data points (or a series of data points) that can be spaced at various lengths of time. For this reason, unless your data points are VERY close together, radar will always be a more accurate measurment of velocity -- and it's also how you COULD have a radar gun showing one speed while GPS calculates another....
I thought /. was supposed to be US-based. Why then are we getting articles with "defence" and "mum" in the titles? Those are both UNAMERICAN!
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.
John Walsh once found me while looking for some other kid. He was not amused.
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!
I am government man, come from the government. The government has sent me. -- G.I.R.
In addition to that small change why can't the radar gun be fitted with a camera so that the LEO can prove in court that he was in fact aimed at the correct vehicle. My uncle told me about an incident from his youth where a car in front of him was speeding and was clocked by an LEO in an oncoming car. The speeder turned right as soon as the LEO passed (the LEO had to turn around and go around traffic to get back to where he though the speeder was in line). My uncle got pulled over based on the other guy's speeding because they were driving similar looking vehicles. A camera aimed down the barrel of the radar could have proven that the clocked car was no my uncle's car.
2 fairly simple things LEOs could do to make their work more verifiable. The first adds little cost. The second is another video feed to record and that adds more cost. Both would be extremely useful though.
This is not universally true. In DC, they have photo speed enforcement mounted on vans and police cars. I doubt those vans are cutting holes in the road every morning when they set up.
They don't grade fathers, but if your daughter's a stripper, you fucked up. --Chris Rock
I'm going to summarize what you wrote as follows: I work in marketing for Decatur Electronics, and our products are infallible.
It turns out I've heard way too many technology marketers have way too inflated levels of confidence in their wares to take any of what you say at face value.
Here's how I look at it. A GPS unit knows its location to within a few feet. A GPS's clock is synced to the atomic clock. At that point, it's a simple division problem to get the unit's velocity.
On the other hand, there are many documented situations in which police radar is wildly inaccurate (my favorite quote of yours was "those guns have an internal lockout in case of malfunction". I mean really, if the unit is malfunctioning, how can it know that it is malfunctioning? It's malfunctioning, for pete's sake!), and there are a lot of things that have to go right for police radar to be accurate.
This is why I'd be much quicker to believe a GPS unit than a radar unit.
They don't grade fathers, but if your daughter's a stripper, you fucked up. --Chris Rock
I think there is something here that you are not telling us. I've fought two tickets and won them both, and I never had to pay a dime. Certainly not $10,000.00.
What is the real story here?
They don't grade fathers, but if your daughter's a stripper, you fucked up. --Chris Rock
"Speaking as a traffic engineer"
Maybe you shouldn't.
I have personally seen ALL of the things you say the cops won't do, or can't do, and have seen people lose their cases as a result.
I don't believe you're a traffic engineer, but even if you are, you're lying about everything else.
In all seriousness, you'd better learn WTF you're talking about or stop giving advice, cause you're full of shit.
"Believe me!" -- Donald Trump