ARLA/CLUSTER: GPS versus Radar.

João Gonçalves Costa joao.a.costa
Quarta-Feira, 7 de Novembro de 2007 - 14:09:23 WET

Os pais de um jovem condutor norte-americano depois de sofrerem várias multas por excesso de velocidade praticadas pelo seu filho resolveram meter a policia em tribunal contentando o excesso de velocidade  no Radar com os dados contraditórios registados no seu GPS, solicitando que o tribunal ateste qual é o sistema com maior precisão. Independentemente desta questão, quantos radares usados pela policia e existentes nas estradas são devidamente calibrados e aferidos periodicamente..? Será que não poderemos usar um sistema de APRS para contestar as multas que nos são aplicadas...?

João Costa

GPS vs. radar accuracy
Stepdad is contesting a teen driver's speeding ticket.
By Lisa Leff

Associated Press

WINDSOR, Calif. - Given the option of contesting a traffic ticket, most motorists - 19 out of 20 by some estimates - would rather pay up than pit their word against a police officer's in court.
A retired sheriff's deputy nevertheless hopes to beat the long odds of the law by setting the performance of a police officer's radar gun against the accuracy of the GPS tracking device he installed in his teenage stepson's car.

The retired deputy, Roger Rude, readily admits his 17-year-old stepson, Shaun Malone, enjoys putting the pedal to the metal. That's why he and Shaun's mother insisted on installing a global positioning system that monitors the location and speed of the boy's Toyota Celica.

Malone complained bitterly about his electronic chaperone until it became his new best friend July 4, when he was pulled over and cited for going 62 miles per hour in a 45-m.p.h. zone.

Rude encouraged him to fight the ticket after the log he downloaded using software provided by the GPS unit's Colorado-based supplier showed Malone was going the speed limit within 100 feet of where a Petaluma officer clocked him speeding.

"I'm not trying to get a guilty kid off," Rude said. "I've always had faith in our justice system. I would like to see the truth prevail, and I would like Shaun to see that the system works."

Although traffic courts do not routinely accept GPS readouts as evidence of a vehicle's speed - and many GPS receivers aren't capable of keeping records anyway - some tech-savvy drivers around the world are starting to use the technology to challenge moving violations, according to anecdotal accounts from defense lawyers and law-enforcement officials.

This summer, for instance, an Australian farmer became a hero to speeders everywhere when he got a ticket dismissed after presenting police with data from his tracking device.

While winning a case this way is far from a sure thing, GPS-generated evidence could at least inject an element of doubt into typically one-sided proceedings, said Jim Baxter, president of the National Motorists Association.

A Sonoma County traffic commissioner is expected to rule early this month whether to dismiss Malone's ticket based on Rude's written argument that the motorcycle officer's radar gun was either improperly calibrated or thrown off by another speeding car.

"Radar is a pretty good tool, but it's not an infallible tool," said Rude, who spent 31 years in law enforcement. "With the GPS tracker, there is no doubt about it. There is no human interference."

Rude plans to offer scientific data and experts if his challenge doesn't succeed right away.

Petaluma police Lt. John Edwards said he could not discuss Malone's case, but disputed Rude's contention that GPS is more accurate than a speed gun.

"GPS works on satellite signals, so you have a delay of some type," Edwards said. "Is it a couple-second delay? A 30-second delay? Because in that time, people can speed up, slow down."

The device in Malone's car, originally designed for trucking companies, rental-car agencies, and other businesses with fleets, sends a signal every 30 seconds that records his whereabouts and travel speed.

His parents signed up to be automatically notified by e-mail whenever he exceeded 70 m.p.h., and the one time he did, he lost his driving privileges for 10 days.

Rude said he was talking about the ticket - Malone has tried to stay out of it - to encourage other parents to keep tabs on their teenage drivers using GPS. He said he has had to tell too many parents that their child was killed in a wreck.

David W. Brown, a Monterey lawyer and author of Fight Your Ticket in California, said attacking the reliability of radar guns does not usually get speeders very far, especially if they are unwilling to devote extra time and money to hiring legal experts.

Still, among people who do challenge tickets, the proportion who triumph is relatively large, he said. Their technique? Betting the officer who cited them will be unable to make it to court.

"Statistically, when people do prevail," Brown said, "that is the most common method."

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