GPS Data Used To Disprove Radar Gun In Speeding Trial

from the not-so-fast dept

Fri, Jul 18th 2008 4:11pm — Kevin Donovan

Over the past couple months, we've pointed to the misuses of technology to enforce traffic laws, particularly red light cameras which often end up causing more accidents or allow municipalities to decrease the yellow light time and increase ticket revenue. Last fall we noted the case of a teenager who was challenging another technological traffic enforcement: radar guns -- and he was using a different technology to do so: his GPS system. Now, the 18-year old driver has successfully contested that speeding ticket which he was issued for allegedly traveling 62 mph in a 45 mph zone.

Luckily for the teen, his car had an advanced GPS system which not only provided directions but measured velocity to "within 1 mph." After receiving a trial and bringing a GPS expert to testify to the accuracy of the device, the $190 ticket has been dismissed. What is not clear is why the police officer's radar gun output was more than 1/3 inflated (though this is hardly an isolated incident). Also, as a number of people have pointed out, similar GPS data, if widespread, could also come to serve as critical evidence in convicting traffic law violators instead of providing a check on state authority.

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Filed Under: gps, radar guns, speeding tickets

45 Comments

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Larry969, 18 Jul 2008 @ 5:03pm

GPS accuracy
I will say this for GPS. I LOVE it to death. BUT, anyone who uses one for more than just a lil bit will come to understand that there is a flaw in the system.

I have "while sitting at my computer with GPS hooked up" made a few trips to far away places... I once made a trip 'while sleeping' to Antarctica and back in less than 30 min.

When I woke up and looked at my computer screen, I thought DAMN I'm good. A trip to the South Pole and back while I was asleep. Can you get any better than that?
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The Truth Beacon, 18 Jul 2008 @ 5:07pm

Re: GPS accuracy
The reason for that is GPS requires motion for accuracy. When it is standing still, it more-or-less freaks out after a while...
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Tim, 18 Jul 2008 @ 5:41pm

Radar Accuracy
I lost all faith in Radar speed checks years ago.

I used to regularly have lunch with an officer and he'd bring a portable radar unit sometimes. We'd routinely clock dumpsters and trees at anywhere from 50 to 300 miles per hour, and most cars exiting the drive-thru of the burger joint were clocked in at 45 MPH or so when they were moving at a walking pace.

Seems that the cops should use the units that MLB has for clocking pitches.
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Anonymous Coward, 18 Jul 2008 @ 5:50pm

Re: GPS accuracy
GPS does not require motion for accuracy. GPS is based on Time Difference of Arrival. It requires at least 3 satellites to determine position, and a 4th for altitude.

The way the satellites are positioned and orbiting, 5-7 are technically "visible" at most locations, however due to the very low broadcast power and small antennas on hand-held units, often only 4 or 5 are picked up.

If it drops to 2, which is the case in a house, building, underground, etc, then it can only isolate your position to either of TWO intersections of arcs, which would be why it would go from wherever it was to Antarctica.

Next time, don't be such an obtuse dolt and expect a 1" antenna to pick up signals from satellites orbiting at 12,500 or so miles away while inside your house.

Car based GPS assumes you are on a road, and uses that fact as another variable to determine location, eliminating a good bit of error, and while on the dash of a car, likely picking up 6+ signals, the accuracy of speed estimations is more like 1/10th of a MP/H or less, and doesn't suffer from multi-path distortion like radar/lidar does.
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Calibrater, 18 Jul 2008 @ 6:03pm

6 months ago I contacted Garmin, TomTom, and a couple others about certifying GPS data for court use. I currently certify Radar and Speedometers for Law Enforcement and evil speeders. Every manufactuer gave me the same answers. You cannot certify the Data or the Instruments on retail store GPS units, because at any given moment they can be as much as 100% inaccurate due to different enviormental conditions.
But the data from the high end GPS units such as those in law enforcement fleets can be certified within 1%. Luckily for the teen, his car had an advanced GPS system which not only provided directions but measured velocity to "within 1 mph." Sounds like a $2000.00 GPS unit to me.
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Anonymous Coward, 18 Jul 2008 @ 6:22pm

Also, the radar units must be calibrated every once in a while, ideally once per patrol. Golden Eagle brand units come with a tuning fork to do just that, but no one ever tunes their radar unit.
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The Arbiter (profile), 18 Jul 2008 @ 8:16pm

Re: Radar Accuracy
Then he was using it wrong. Hand held units are susceptible to panning, which does not affect vehicle mounted unites. If properly used RADAR is very accurate
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The Arbiter (profile), 18 Jul 2008 @ 8:22pm

Re: "tuning" RADAR
You don't know much about RADAR operation. Police traffic RADAR units are supplied with tuning forks. They do not "tune" the unit. They are a calibration test. You have 2 forks that are calibrated to vibrate at a given frequency. You strike them on something like the heel of you shoe, hold it in front of the RADAR antenna and verify that the unit reads the speed associated with that frequency. And any officer operating the unit properly, checks his unit before ad after each stop. And most departments will be very good about making sure they have up to date calibration sheets.
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Lawrence D'Oliveiro, 19 Jul 2008 @ 2:29am

Re: "tuning" RADAR

...hold [the tuning fork] in front of the RADAR antenna and verify that the unit reads the speed associated with that frequency.

Except the maximum speed at which the fork is moving will depend on the amplitude of the oscillation, not just the frequency. And there's no easy way to ensure the amplitude is constant.
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English, 19 Jul 2008 @ 7:35am

Re: Re:
Your credibility is highly suspect when you can't even write a coherent sentence.
If you were to try composing a proper sentence while belittling other poster's comments, the casual reader just might think you are knowledgeable on the subject matter.
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Anonymous Coward, 19 Jul 2008 @ 7:51am

Key words "officer operating the unit properly, checks his unit before ad after each stop".
I worked for a small police department in upstate NY. In the five years that I worked there, not one officer checked his unit prior to the beginning of his or her patrol. The vehicles were checked for damage, but the radar units were not. Even the supposed traffic units, the low profile wonders that would generate more income for the town did this.
What I especially liked was the fact that one of my friends is a radiohead, has more antennas coming off the roof of his vehicle than a porcupine. He was stopped by an officer, citing the fact that he was speeding. When my friend started questioning the officers radar unit and its calibration, the officer quickly backed off, and let him go. It didn't help that my friend also had a radar unit sitting in his windshield at the time. And yes, he is licensed for it, since radar is essentially a radio that transmits and receives its own broadcasts.
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Anonymous Coward, 19 Jul 2008 @ 7:51am

Key words "officer operating the unit properly, checks his unit before ad after each stop".
I worked for a small police department in upstate NY. In the five years that I worked there, not one officer checked his unit prior to the beginning of his or her patrol. The vehicles were checked for damage, but the radar units were not. Even the supposed traffic units, the low profile wonders that would generate more income for the town did this.
What I especially liked was the fact that one of my friends is a radiohead, has more antennas coming off the roof of his vehicle than a porcupine. He was stopped by an officer, citing the fact that he was speeding. When my friend started questioning the officers radar unit and its calibration, the officer quickly backed off, and let him go. It didn't help that my friend also had a radar unit sitting in his windshield at the time. And yes, he is licensed for it, since radar is essentially a radio that transmits and receives its own broadcasts.
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Paul`, 19 Jul 2008 @ 8:25am

This remind me a bit of something that happened where I live a while back. A woman was finned for doing 120kmph in a 80 zone by a fixed radar gun on the freeway even though the car she was driving maxed out at around 80kmph.

She rang a local radio station which took the car to the local race course and got a professional driver to push the car to see the max speed they could get and it was about 85kmph.

A few month later after about everyone who had been issued a fine for speeding on that strip of road appealed they tested the guns and found they were wrong more often then not.
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Mike, 19 Jul 2008 @ 9:19am

FYI
If you don't hold a radar gun still, you can cause higher readings, I can make a stopped car do 300 every single time...
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Public Relations, 20 Jul 2008 @ 2:54am

The sad thing is that the teen had to bring an expert to trial to testify.

This costs both time and money.

How many hundreds of innocent people chose to pay rather than go through that hassle - or because they did not have an advanced GPS system.

Hopefully, this wont end here - a class action suit would be appropriate if negligence can be proved on the part of the municipality.

That is the only way they will be motivated to change.

According to this blog - they do not even know why the Officer was receiving the wrong info - nor is there any indication that they will look into any other cases involving that Officer or that technology they are using
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TheDread, 20 Jul 2008 @ 9:31am

GPS Data Used To Disprove Radar Gun In Speeding Trial
Many years ago I was stopped for speeding in a speed trap. The newly incorporated city in which this happened was just starting to use radar gun traffic enforcement. They were using Doppler field effect radar guns which at the time were required by state law to be re calibrated after each traffic stop.

When I went to court for the citation before pleading I asked the Judge If recalibration was required between traffic stops, he replied that this was the case. I then asked if it was possible to recalibrate the gun between stops and issue 3 citations within 3 minute, my being the third citation by the officer wielding the radar gun within this time period, He stated it was not. My case and the case of the second person cited in the speed trap were dropped.

He then called the officer,who was in court for an unrelated matter. to the bench and had the bailiff clear the court. Once outside everyone could here the Judge berating the officer.

I was actually speeding slightly doing 30 mph in a 25 mph zone the citation was for 45 mph. An officer in a neighboring municipality I was friends with told me of the re calibrations mandated between stops saving me from having to pay an erroneously inflated fine - 5 mph versus 20 mph over the limit.
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John (profile), 20 Jul 2008 @ 1:41pm

The cost?
Like poster #15 mentioned, how much money did it cost for the guy to hire a GPS expert to testify in court?
Wouldn't it have been cheaper just to pay the ticket?

Then again, this is what too many police agencies count on: people will simply pay the fine because it's cheaper and easier than fighting in court.
Are the radar guns accurate? Who knows, since no one's challenging them.
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Anonymous Coward, 20 Jul 2008 @ 2:42pm

So glad we are so anti-police on here now
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Anonymous Coward, 20 Jul 2008 @ 4:25pm

Re: GPS Data Used To Disprove Radar Gun In Speeding Trial
The newly incorporated city in which this happened was just starting to use radar gun traffic enforcement. They were using Doppler field effect radar guns which at the time were required by state law to be re calibrated after each traffic stop.
ALL speed RADAR uses the Doppler effect to determine speed, nothing is unique about that. What I find hard to believe is that a state law would require that the units be recalibrated between stops. That is hard to believe because federal regulations restrict those who can service and calibrate those units to persons who possess federal licenses (and special equipment) for doing so. Very few police officers possess such licenses and equipment so such recalibration would require a trip to a service location after each stop. It seems highly unlikely to me that the state would require such a thing. What state was this supposedly?

Note that recalibration is a very different thing from a quick calibration check (which officers can do).
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Anonymous Coward, 20 Jul 2008 @ 4:33pm

Re: Re: "tuning" RADAR
Except the maximum speed at which the fork is moving will depend on the amplitude of the oscillation, not just the frequency. And there's no easy way to ensure the amplitude is constant.
True, but irrelevant. It is the frequency of the vibrating fork (as long as the amplitude is sufficient) that is used in the quick check procedure to simulate a Doppler shift, not the speed of the forks.
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Anonymous Coward, 20 Jul 2008 @ 4:36pm

Re: Re: Re:
...the casual reader just might think you are knowledgeable on the subject matter.
The casual reader is invited to do their own research and find that The Arbiter was correct.
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Anonymous Coward, 20 Jul 2008 @ 4:48pm

He was lucky.
He was lucky. I've know of judges at the traffic court level to sit and listen to a court-certified, PhD forensic engineer expert witness explain how what the officer claimed to have observed was physically impossible. After which and without explanation the judge SIMPLY proceeded to bellow out "INADMISSIBLE! GUILTY! NEXT CASE!" as he brought the gavel down. Just proving that you're innocent doesn't count for much in Texas traffic courts.
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Anonymous Coward, 20 Jul 2008 @ 4:53pm

Re:
So glad we are so anti-police on here now
How so? What are you, fascist?
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Calibrator, 20 Jul 2008 @ 5:16pm

It is law in most states to have radar, laser and speedometers used in law enforcement each be tested, calibrated and certified every 6 months. If a lawyer asks for the certificates in court and the officer cannot produce any from within 6 months, ticket is dismissed. Same can be said for a civilan with a speeding ticket, if you can prove your speedometer was inaccurate and you have since had it repaired and certified, ticket dismissed (in most cases if your not an arrogant fuk) It ALWAYS boils down to the judges. If the judge has a bad day so will you.
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Anonymous Coward, 20 Jul 2008 @ 8:26pm

Re:
Same can be said for a civilan with a speeding ticket, if you can prove your speedometer was inaccurate and you have since had it repaired and certified, ticket dismissed (in most cases if your not an arrogant fuk)

I wish. I had an inaccurate speedometer, got a ticket, got it repaired, then went to court with the repair receipt. The judge said "That's no excuse. The law doesn't even require you to have a speedometer. Guilty". The same thing has happened to other people I've known and the court has never dismissed their tickets because of faulty speedometers.
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David McMillan, 20 Jul 2008 @ 9:19pm

Re: Re: "tuning" RADAR
"They do not "tune" the unit. They are a calibration test."

hmmmmm... tuning is a type of calibration.

Granted saying "calibration is tuning" is not an equally true statement. How ever because of the similarities you can not blame some one for minor error in semantics.
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Anonymous Coward, 21 Jul 2008 @ 6:33am

Re: Re: GPS Data Used To Disprove Radar Gun In Speeding Trial
"Note that recalibration is a very different thing from a quick calibration check (which officers can do)."

A discerning reader, then, might assume that a quick check was the actual requirement.
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Anonymous Coward, 21 Jul 2008 @ 7:40am

GPS data
I'm glad this guy won but I'm a little suprised. His defense is basically that it's impossible that I've sped because my GPS indicates that I've traveled X distance in Y amount of time. This does not take into account the fact that he may have been going over the speed limit for some short period (and got caught) and also going under the speed limit for a short time.
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Pinky Floyd, 21 Jul 2008 @ 8:45am

Re: GPS accuracy
I hope it was more pleasant for you than me...It was -112 F below when I landed there (was there for 23 miserable hours doing an inventory..)

I couldn't leave fast enough.
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Anonymous Coward, 21 Jul 2008 @ 11:04pm

Re: Re: Re: GPS Data Used To Disprove Radar Gun In Speeding Trial
A discerning reader, then, might assume that a quick check was the actual requirement.
That's very different from what was claimed. A discerning reader, then, might assume that the post was from an unreliable source and disregard the whole thing.
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Anonymous Coward, 21 Jul 2008 @ 11:09pm

Re: Re: Re: "tuning" RADAR
hmmmmm... tuning is a type of calibration.
"Testing" is not. And truthfulness is not just a question of "semantics".
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Anonymous Coward, 22 Jul 2008 @ 5:11am

Re: Re: Re: Re: "tuning" RADAR
""Testing" is not. And truthfulness is not just a question of "semantics"."

Lighting yourself on fire while eating animal crackers is also not a type of calibration. And because I'm responding to a poster chastising another for switching the terms tuning and calibration I fail to see the point of your comment.
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GPS Tracking, 24 Jul 2008 @ 11:42am

Tracking - not navigation
This story is about GPS tracking. It's not a GPS navigation device that sits on the dash of a vehicle and gives turn-by-turn directions.
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Tracking Devices, 4 Aug 2008 @ 11:59am

gps tracking
There are several human error factors with radar:
1) Clocking the wrong vehicle when there is more than one vehicle or in a passing situation.
2) Stationary or Mobile radar. Stationary is much more accurate because the radar is not having to calculate the police car speed.
3) Catching and identifying the right vehicle that was speeding. This can be especially difficult while running stationary radar because of the delay of pulling out into traffic to chase after the suspect vehicle.
4) Radar calibration, which should occur at least once per year. This should not be confused with an officer checking calibration with tuning forks. The calibration should be checked before and after each ticket is issued, but at a minimum, at the beginning and end of the officer's shift.
5) Hills and turns in the road can easily affect radar readings. Radar should not be run around hills and turns. I have seen radar indicate (for a few seconds) speeds of several hundred miles per hour when it was obvious the vehicle was only traveling at a speed of maybe 50 - 75 MPH.
6) A/C or heater fan can interfere with radar readings.
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Susie Harris, 22 Sep 2008 @ 9:45pm

Radar guns and speeding ticket
Hi,
Recently, as I traveled down a desolate hyway in Arizona, I put my cruize control on 65 like always as that is the speed limit and, my car does not favor doing anything over that, it shakes and shimmies and is comfy doing 65.
Suddenly, I saw red flashing lights behind me and thought "I beter pull over, this cop is probably going after the big rig about 10 car lengths ahead of me, hauling but.
Not so, the cop was red lighting me and for what?
Speeding, specifically 81 in a 65 MPH zone.
Is it possible his radar gun was picking up the truck?
My car is so short, approximately 35-40 inches tall from the ground.
I am going to court tomorrow, just wanted to see if anyone has a comment
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pat, 5 Jan 2009 @ 12:50pm

Re: Radar guns and speeding ticket
hello susie. just wanted to check how you came out with your court date on the speeding ticket. i had the similar experience yesterday, being clocked faster than i was actually going. i plan to contest this, but i still have a couple of weeks. any suggestions? thanks.
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Jack L. Darrington, 21 Jan 2009 @ 3:05pm

Speeding Ticket
I RECEIVED A SPEEDING TICKET BACK IN 2008, AND OF COURSE I CONTESTED THE TICKET IN CITY COURT AND NOW IT IS GOING TO COUNTY COURT. THE MOST AMAZING THING TO ME WAS THAT THERE WERE THREE CARS IN THE LEFT LANE AND I WAS IN THE RIGHT LANE GETTING READY TO MAKE THE NEXT RIGHT TURN COMING UP. ME AND THE LAST CAR WERE SIDE BY SIDE AND THE SUV AND THE OTHER CAR WERE IN FRONT IN THE LEFT LANE. THE NEXT THING I SEEN WAS THE POLICEMAN WAVING ME TO THE RIGHT AND I THOUGHT THAT THERE WAS SOME TYPE OF ROAD WORK OR THE LIGHT WAS MALFUNCTIONING I WAS PULLED OVER GIVEN A TICKET FOR SPEEDING ASKED THE FEMALE POLICEMAN CAN I SEE WHAT MY SPEED WAS AND SHE TOLD ME NO "I DON'T HAVE TO SHOW IT TO YOU. I'VE HAD A SPEEDING TICKET BEFORE AND THE POLICEMAN NEVER SAID THAT. THIS WAS IN THE CITY OF LAWRENCEVILLE, GA. ANY SUGGESTIONS FROM ANYONE. I THINK THAT THE SUV WAS CLOCKED.
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daveb, 3 Feb 2009 @ 5:43am

Re: Re: GPS accuracy
Your statement is simply not true. The GPS can measure your speed, including whether or not you are moving. If you are not moving, then your speed is zero. This is true whether or not you have a GPS with you.

The only questionable measurement while not moving is "direction", since direction measurement requires movement, it is not possible to return a value when the speed is zero.

If you have a GPS that "freaks out after a while" you might want to have it repaired.
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ashley, 16 Jun 2009 @ 1:05pm

Re: Radar guns and speeding ticket
to susie harris: what happened in court, the exact same thing happened to me...
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دردشه, 5 Jul 2009 @ 11:30am

This story is about
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The Arbiter (profile), 28 Sep 2009 @ 9:12pm

Re: gps tracking
1- Not a RADAR problem, that is an operator issue
2- Not true. They are equally accurate. Not sure where you got this tidbit from.
3- This is a training issue, identification of suspects is a fundamental element of police training.
4- Most states require certification for the device and the tuning forks every 6 months, and yes, the device should be tested with the calibration checks before and after each stop.
5- Hills affect the RADAR only when the target vehicle is behind the hill crest and a reading is not possible. Turns do not affect the RADAR except in the case of cosine angel effect, which is to the benefit of the driver, not the officer.
6- True..to some extent, but this is dealt with in two ways a) Training the officer to recognize ghost readings (which is a fairly easy thing to do) and b0 equip the vehicle with a proper dash mount for the device to shield the antenna from the fan openings in the dash
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The Arbiter (profile), 28 Sep 2009 @ 9:15pm

Re: Speeding Ticket
You can of course tell the judge your side, but she was correct, most states do not require the officer to "lock in" the speed to show to the violator. In fact, to do so affects the tracking history that the officer must testify too in court
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Jay D. Anderson, 11 Jan 2012 @ 11:15pm

Inaccuracy of RADAR
Use of Police RADAR for speed detection requires some subjective analysis. The RADAR "beam" is a "Cone" that widens dramatically and it cannot be focused on a single vehicle (like LIDAR can). Therefore there are settings for "fastest vehicle" and this generally the setting Police use. There for the Police Officer must try to ascertain which vehicle in the cone is actually traveling the fastest (the one they got the reading from). That is VERY VERY hard to determine when a vehicle is moving towards or away from the Officer point-of-view. Also the cone may pick up the speed of much larger object much further away and the officer can easily attribute that speed reading to a closer object that they are focused on. Probably the reason my daughter got a ticket for going 45 MPH in a 25 MPH zone when she had been stopped at a red light and had just stated moving (5-10 MPH). What happens in court? Judge asks for calibration info and asks Officer about their training... good enough... GUILTY. These days being found guilty doesn't mean you are not innocent... just that they are sticking you with the conviction. Why? Because they can.
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Andrew, 29 Jan 2016 @ 3:00am

GPS is not always accurate
GPS speed records might be very inaccurate around overpasses or areas with three canopies. Up to 20 km/h speed difference might be observed between the true speed and GPS. This was verified numerous times by accredited labs. Your so called GPS expert is a joke
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Tom Scott, 13 Jun 2017 @ 3:49pm

More than GPS - Fighting the Corrupt System
For those of you who want to protect yourself, register at the bottom of www.stloiyf.com/blog to get part 1 of our book for free. It's the #1-rated legal guide for Americans on Amazon. Our heaviest chapter is traffic law.
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