Accused speeder to cops: My GPS proves your radar gun is wrong
GPS-based tracking devices don’t just help you figure out where you are and where you’re going, they might also help you avoid a speeding ticket. Shaun Malone of California is contesting a speeding ticket in that state by arguing that his GPS-based tracking system shows that the officer’s radar gun was wrong.
Malone, a 17-year-old who was clocked doing 62 MPH in a 45 MPH zone on July 4 of this year, has more than just a GPS on his side. As the AP reports, his stepfather Roger Rude is a retired sheriff, and is pushing Malone to fight the ticket. (As an aside, how awesome would it be to be Sherriff Rude?)
Ironically, Malone’s parents had the GPS system installed in order to track the whereabouts and speed of their son, whom they readily admit has a lead foot.
The debate is likely to come down to how often the GPS device calculated and reported ground speed. Petaluma police lieutenant John Edwards told the AP that since GPS is satellite-based, there’s a delay involved, and that Malone may have sped up and slowed down in the window between measurements, which could be as long as 60 seconds.
Here’s an Aussie that did it, too.
GPS definitely doesnt always catch spikes in speed, I know I went at least 10 over the “max” mine has recorded
#1 That depends on how often it records the speed. There are some on the market that record every 1/5th of a second. That would be overkill for speed monitoring.
Seems like a long shot, but maybe the kid can confuse the judge enough to get out of it. Dr. Hunter Cashdollar
How about aircraft quality sampling rates — accurate to 0.5 knots at 300+ knots GS and 3 to 4 feet 3D position. But my goodness, it’s not cheap!
I didn’t know any car GPS units had a print-out.
As a lawyer here in Australia I have had a few inquiries about GPS being used. GPS is not as accurate as people make it out to be. As the police correctly point out, there is a delay.
However, you will generally find that a GPS in open space will show that your speed is about 5kph (3mph) slower than your actual speed on the speedo. Doing sudden speed accelerations is the same i.e. inaccurate reading, but the very fews cases show this is in a built up area i.e. where the signal can be blocked by tall buildings etc.
The police do not accept GPS anymore as a defence and in fact will fight it all the way to set an example.
#6: Maybe in Australia the defense won’t work, but I believe a GPS defense can work here in the states.
I recently got a ticket for doing 84 MPH in a 75 MPH zone. I knew I wasn’t speeding according to my speedometer, but a timed mile showed my speed at an indicated 75 MPH to actually be 84 MPH.
I called several places including the car dealer to see about checking my speed; all of them told me to use GPS to determine accuracy.
The Garmin in my 4 cylinder Escape has recorded a max speed of 350 mph. Must have been the day I lent the car to a friend.
#8, Tom;
Ah, yes. As pointed out in the ArsTechnica forums, GPS isn’t flawless and can be impacted by terrain, bridges, trees, buildings, etc. However, when it’s wrong, it is usually very easy to tell when it’s wrong.
Radar does the same thing, too. When acquiring a target, the reading can initially fluctuate from negative MPH (usually given as an -E- for Error) to many 10s of MPH over the target car’s actual speed. This is especially true in heavy traffic. Overzealous cops can lock down a reading prematurely, especially if they want to specifically target that red sports car…
And don’t forget that certain radar modes, such as POP, are not allowed by the courts for legal speed measurements.
Odd. My old Garmin reacts within one second to speed changes while driving. It reports about 1mph lower than my digital speedometer, and seems to be nearly as reactive as the one tied to the wheel.
I always assumed that it was the more accurate, reporting 0.1 mph variations. On cruise control it is +/- 0.2 mph stable.
At rest, it reports speeds up to 2mph at startup, but then settles. One would assume that this decade old device was WAY less capable than current models.
Would anyone know how I can extract the log file on a Garmin nuvi 300?