What do cops think about this? A real way to fight speeding tickets?

Question

http://arstechnica.com/news.ars/post/20080718-nabbed-for-speeding-gps-data-could-get-you-off-the-hook.html

Its strange that NO COP wants to believe if i say i have gotten 'incorrect speeding tickets'. Finally there is some scientific defense!

The sad thing is that a SCIENTIST really went and LIED about the accuracy of GPS devices in the case above! The sad truth is that GPS is not as prone to 'user error' as the typical police radar gun! Once the GPS is correctly installed, its accuracy is fairly 'constant'.

What are your thoughts on this?

Answer 1

What scares me is that they will then be able to read the GPS and the sector you are driving in and have a speeding ticket mailed directly to you without being pulled over or even knowing that you were busted.

Answer 2

First of all....ALL equipment is subject to being faulty!

This particular "device" is a system on the market where parents can "watch" their siblings from the home computer. It is based upon the GPS Tracking systems and fairly accurate.

Radar detection is extremely accurate and  its information is up to date and immediate whereas the GPS tracking is not. At least not with the system used by this particular commercial company.

You'll also learn that the only "accurate" GPS systems are those of the military whereas the civilian models are SLIGHTLY altered!

A very interesting argument, however, I believe the case will be remanded back to the original courts decision!

Answer 3

If you are following the speed limits, why worry. I have yet to see or hear of an officer pulling someone over that was not exceeding the speed limit by 5 mph or more.

Stop trying to beat a ticket and just obey the laws.

Answer 4

> This case presents MORE THAN reasonable doubt about the ticket.

Maybe maybe not. I used to work for Nasa, creating and implementing algorithms for measuring satellite attitudes in orbit, to accuracy way more then this article talks about. After all, if the satellite is not facing exactly where you want it, the scientific instruments are useless.

So I feel comfortable evaluating such claims, but so far I haven't seen any real evidence, just anecdotal reports about both technologies.

I have never doubted I could create reasonable doubt were I ever caught for speeding with radar, which has never happened. So I am not saying it is infallible.

But neither is GPS - we know that the satellites are DOD, that signals commercial use is deliberately obfuscated slightly, and that relying on a single signal (there are 2 or more IIRC) leads you to an error estimating a stationary position in 2 dimensions to somthing like, I forget, but lets say a foot over 100 yards, or .03% more or less. And that is not for a quick moving device - even  cell phones require amazing engineering to stay in touch at those speeds. How do we know the GPS can do it successfully? We don't, really.

I am not saying it is not possible, but without testimony to indicate how the GPS devices work, and frankly without examining the source code and the actual devices, there is no way to know if there is a programming error or not.

As long as either device has proprietary components, we can't really rule out bugs in the system.

17 MPH is a big discrepancy for competing technologies.

I think either is subject to error.

The better approach for the reporter would be to repeat specific testimony and toss it out there for the nerds of the world to test.

I suspect that will happen soon enough though.

Answer 5

i think its illegal.

Answer 6

Don't forget, though, that it's a double-edged sword.  They can now also subpoena GPS records to prove that you WERE speeding!  :-)

Answer 7

A GPS unit will tell WHERE you are, a radar unit will tell HOW FAST you are driving.   The ticket is for speeding, not in being in the wrong place.

Pay the ticket!!

Answer 8

First ... I am not a police officer.  Second ... I am not a GPS technician or a rocket scientist.

It sounds like this type of GPS just collects positioning data at a regular interval ... every 30 seconds.  It uses this data to determine the ESTIMATED speed of the vehicle.

So if your vehicle moved 1/2 mile between 30 second data collections ... the estimated speed of your vehicle is 60 MPH.

Fine if you are on a straight, level road.  What about if you are on a road with steep inclines and a lot of curves?  The datapoints collected would STILL show that you are traveling 1/2 mile per second ... estimated speed 60 MPH ... but you actually drove at 73 MPH to make the distance ... because you are not traveling in a straight, level line.

It is possible for both the police radar and the GPS unit to be right ... according to how they collect data!

EDIT:  

Here is an example of what I'm talking about.

The GPS data shows a car moved between two points 1/2 mile apart in 30 seconds ... estimated speed 60 MPH.

The road is a curve around an obstruction (lake, mountain, etc).  The driving distance would be about 1/2 the circumference of a circle with a diameter of 1/2 mile (2,640 ft).

Circumference = [pi] * 2640

Circumference = 8293 ft.

Raod distance = 8293/2 or 4146.5 ft

4146.5 ft = .785 miles (let's round DOWN to .75 miles!)

driving .75 miles in 30 seconds would mean traveling at 90 MPH (.75 * 120).

The GPS data would be correct (according to how it collects data), the officer's radar gun would also be correct if it recorded a speed of 90 MPH during that time.  Both systems correct in their own way.  I saw nothing at the website (www.rmtracking.com) that involved having the GPS unit tied into the speedometer of the vehicle ... in fact installation is done by the purchaser!

Answer 9

Every speeding ticket is up for debate.  The radar needs to be calibrated just like anything else.  The same will happen with the GPS system.  This will all go away and everyone will continue to get their speeding tickets whether they were speeding or not.