Accused speeder to cops: My GPS proves your radar gun is wrong

[johnnymk]

http://arstechnica.com/news.ars/post/20071026-accused-speeder-to-cops-my-gps-proves-your-radar-gun-is-wrong.html

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. In fact, he has already been grounded for having gone over 70 MPH after the GPS was installed. Nevertheless, Malone's parents say that the data on the day in question shows that their son was not speeding in the vicinity of where the ticket was issued.

While many GPS systems don't log travel details extensively enough to be used as a defense against a moving violation, Malone's car was outfitted with a device that could do just that. According to Rude, all recorded plots on Malone's route show him to be driving under the speed limit. At the same time, Rude says, GPS-systems are clearly more reliable than radar systems, which, while good, are "not an infallible tool" and are subject to human error.

A Sonoma County traffic commissioner has to decide whether the GPS system can be accepted as a basis to challenge the ticket, but ex-sheriff Rude is prepared to push his case in court in the event of an unhappy outcome.

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.

GPS tracking systems like the one in Malone's car are becoming an increasingly popular way for parents to keep tabs on their kids, an outgrowth of the initial use of such devices in car fleets and trucking. Many consumer-oriented GPS navigation systems also have these capabilities, but Malone's was hardcore: the system would even e-mail his parents in the event that he drove too fast

[renovation]

i'd be very interested in the out come on this story. i not got a speeding ticket in a long time .knock on wood .not like i shouldn't had. but i use a gps when i do long trips. and twice i would of like to know how fast. i really was going when i was given a ticket. pulling a trailer behind a work truck .on a dirt road that was over loaded. and the second was when i got passed by a cop.on I-75 in ohio when he had to be on a emergency call.becouse he just hit his horn .tip his hat and flue by me .i looked down and it was reading 90 on my speedo . talk about a break i not wanted to seen . what that mess whould of cost me.

[Napoleon54]

The issue is gonna be the refresh rate of the GPS. It's not a realtime measurement like the equipment the cops use. It just records location at two points over time and computes an average rate of travel for A --> B. How quick (refresh rate) is quick enough to be considered accurate for a reasonable estimation of speed at a single point in time?

[Markel]

I think that some states do not give you the option of a jury trial for traffic cases. But I would say that the GPS data certainly interjects a "reasonable doubt" that could keep someone from being declared guilty.

[guiseppewv]

I hope it gets thrown out. Speed tracking devices like radar and lidar are inaccurate if not properly used and calibrated. Plus radar is inaiccurate even if it is calibrated correctly.

[Houdini]

The issue is gonna be the refresh rate of the GPS. It's not a realtime measurement like the equipment the cops use. It just records location at two points over time and computes an average rate of travel for A --> B. How quick (refresh rate) is quick enough to be considered accurate for a reasonable estimation of speed at a single point in time?

Most refresh rates, including on mine, which is a relatively cheap GPS unit, are pretty fast. :shrug: Still, very good point.

Laser is still inherently more accurate than radar, but if not sighted correctly, or not mounted on a very stationary surface, is worthless.

H <----loves his V1

[guiseppewv]

Most refresh rates, including on mine, which is a relatively cheap GPS unit, are pretty fast. :shrug: Still, very good point.

Laser is still inherently more accurate than radar, but if not sighted correctly, or not mounted on a very stationary surface, is worthless.

H <----loves his V1

I love my V1 too. :)

I disagree with the mounting of the laser being tantamount to its effectiveness. I think if the person able to use it is any good at aiming a gun then they won't have any problems hitting a target the size of vehicle. Laser's drawbacks are that it has to be used from a stationary platform (i.e. not like radar which can be used from a moving vehicle), it cannot be used in bad weather (e.g. fog, rain, mist, snow, etc...), it is very difficult to aim at night, and it is legal to "jam" it. The last fact is true because the govt does not control the light spectrum as it does the wavelengths that radio falls into.

[Napoleon54]

I love my V1 too. :)

I disagree with the mounting of the laser being tantamount to its effectiveness. I think if the person able to use it is any good at aiming a gun then they won't have any problems hitting a target the size of vehicle. Laser's drawbacks are that it has to be used from a stationary platform (i.e. not like radar which can be used from a moving vehicle), it cannot be used in bad weather (e.g. fog, rain, mist, snow, etc...), it is very difficult to aim at night, and it is legal to "jam" it. The last fact is true because the govt does not control the light spectrum as it does the wavelengths that radio falls into.

Right. Radar is governed by FCC, which says jamming of communications signals is illegal. Laser actually falls under the jurisdiction of the FDA and 'cause it's not at all similar to signals used for communication, jamming it isn't illegal. Kinda funny since they're used for the same purpose.

[Houdini]

I love my V1 too. :)

I disagree with the mounting of the laser being tantamount to its effectiveness. I think if the person able to use it is any good at aiming a gun then they won't have any problems hitting a target the size of vehicle. Laser's drawbacks are that it has to be used from a stationary platform (i.e. not like radar which can be used from a moving vehicle), it cannot be used in bad weather (e.g. fog, rain, mist, snow, etc...), it is very difficult to aim at night, and it is legal to "jam" it. The last fact is true because the govt does not control the light spectrum as it does the wavelengths that radio falls into.

True. I don't have a laser jammer yet...

Never having had an opportunity to play with one, I've always read that speed laser guns had to be mounted on tripods or rested on windows/roofs/hoods/etc. to be effective. But, as both radar and laser travel at 186,000 miles/sec or so, it doesn't seem like it would matter, as long as the receiving lens on the laser gun is large enough to catch any of the reflected beam (which is, of course, narrower than the radar cone.) So it seems like laser could be used from a moving car, if the guy in the passenger seat were using it and the speed of the cop car could be deducted.

:shrug:

H

[guiseppewv]

True. I don't have a laser jammer yet...

Never having had an opportunity to play with one, I've always read that speed laser guns had to be mounted on tripods or rested on windows/roofs/hoods/etc. to be effective. But, as both radar and laser travel at 186,000 miles/sec or so, it doesn't seem like it would matter, as long as the receiving lens on the laser gun is large enough to catch any of the reflected beam (which is, of course, narrower than the radar cone.) So it seems like laser could be used from a moving car, if the guy in the passenger seat were using it and the speed of the cop car could be deducted.

:shrug:

H

Laser guns cannot be used effectively from a moving vehicle. I was just pointing out that they do not have to be mounted on anything to be effective. The motorcycle cops here in HI use them all the time w/o mounting the laser gun to their bikes.

[Houdini]

Laser guns cannot be used effectively from a moving vehicle. I was just pointing out that they do not have to be mounted on anything to be effective. The motorcycle cops here in HI use them all the time w/o mounting the laser gun to their bikes.

Yeah, I guess I've seen that as well. But, realistically, is there really any good reason that laser detection (basically multiple laser range finder samples and a timer) could not work from a moving vehicle, if the speed of the car with the laser gun is known? Assuming that a lens is large enough to pick up the beam, which is much wider on its reflected path anyway, so that an effective closing speed can be measured, it seems like it could work. I'd bet moving radar, either with a guy in the passenger's seat aiming the gun or with some sort of gimbal setup for single-person use, isn't too far off. :shrug:

H

[thresher]

We did this "GPS" defense for a client - we took my gun (damn fine K gun with more than a few hours of love, but still fully calibrated) and we took three GPS units.
1. The defenders unit (Factory Acura MDX)
2. Garmin Nuvi 200w
3. Tomtom

The results were quite shocking to me, but my friends w/glocks (cop buddies) weren't too surprised.
1 : factory unit - VERY fast waas reading. Damn near real time (within 1/2 second). If you were speeding before I radar'd you, your gps will hang you out to dry. :)
2 : Nuvi 200w - personal unit. Waas reading was once every 1.5 seconds all the way to every 4 seconds. You can beat this unit with your throttle, but what is 4 seconds worth of bliss?
3 : Tomtom - two different units, fellow counselor and my dads :) - Waas reading was dismal. Averaged 4 seconds but went to 10 seconds if conditions weren't "ideal" (read - not in Death Valley)

Our conclusion... The GPS units that are commercially available for retail consumption (under $1000) don't have a memory ability that you can easily re-wind like a dvd or tape recording of your trip. Top speed, average speed, distance etc but no "on the fly" speed. Factory installed units vary by manufacturer BUT Acura can make your details available with a court order. Don't want to get caught speeding? DON'T speed (or buy a gps - the Tomtom 720 will actually tell you where there have been recorded speed cameras!). Want to prove yourself NOT guilty of speeding? Buy a better gps.

Good topic.
One more thing. I went onto http://www.policeone.com/ to see how they were reacting... other than a better video, they're very quiet right now.

[thresher]

One thing about laser (lidar) v Ka radar. You won't see guns running laser "on the go" and it's because lidar is TOO acurate and doesn't "flow" well when used on the go. What it means is: Ka is short burst K band radar. Very easy to aim, VERY easy to control when there is no traffic or light traffic and closing speeds are illustrated in addition to vehicle speeds of both vehicles. Lidar, however, has actually had its beams narrowed to prevent "triple gap" (please just google triple beam lidar so I don't have to explain here :)). Lidar requires a focus or "sharp shooter" lense for the officer to see the lidar beam. You can't do that while driving a car so single "mobile" driver traffic enforcement is out with lidar.

This unit will fix all that. Ladies and gents, my favorite gun on the market: http://www.kustomsignals.com/product_body2.asp?product_id=21&cat_id=10&strpagename=lidar
very fast, very easy and VERY aimable. Oh, did I mention it was expensive? ;)

[Napoleon54]

Hey Thresh,

How much aiming is actually necessary with a radar gun? My understanding is that they throw out a fairly wide beam and just pick up the object that's largest in its field of view. Most cops have thier radar mounted on the dash and drive around with it running all the time. Laser, however, needs to be precisely and deliberately aimed.

Is this correct?

[thresher]

Laser HAS to be aimed very carefully because they have a "scope" included that shows the laser hitting its target. Without specific, flat targets (front license plate is favorite) the laser takes a much longer time to get a positive lock, thus shorter distance.
The dash mounted units are narrow-beam K band. They are designed for one car at a time traffic. Get busted by a dashmount in heavier traffic and its automatic dismissal.
Handheld units other than lidar (laser) are Ka band. Very narrow, very very accurate guns. That dome is designed to narrow the focus even further so you can aim above and sometimes even below (up hills) other traffic to get a good read. BUT, it's all about the gun user. Cop-in-car? Good chance he's not trained with latest unit. Cop-on-bike? Pay the ticket. :)

[Houdini]

Laser HAS to be aimed very carefully because they have a "scope" included that shows the laser hitting its target.

Do they actually have IR screens in the scopes to see the beam or are they simply reticles? I've never had the opportunity to play with one, but I have used laser rangefinders (which are pretty damn cool anyway.)

H

[thresher]

reticles on lesser models, IR screens on the pretty ones. :) They have a new "binocular" unit that is very pretty, works great but no self-respecting department will buy it. Why? You're basically BLIND while using the unit. whoops. http://www.kustomsignals.com/products/prolite.jpg