Shreveport.com - Teen's Ticket Hinges on GPS Vs. Radar

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Teen's Ticket Hinges on GPS Vs. Radar

http://abcnews.go.com/Technology/wireStory?id=3776057

Quote:

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.
Shaun complained bitterly about his electronic chaperone until it became his new best friend on July 4, when he was pulled over and cited for going 62 mph in a 45 mph 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 Shaun was going the speed limit within 100 feet of where a Petaluma officer clocked him speeding.
The device in Shaun'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 mph, and the one time he did he lost his driving privileges for 10 days.

Now this is a good idea, hope it works.:D:D

Mythbusters tried all kinds of ways to beat both radar guns and the lasor guided equivalent (the Lidar). Those devices were impossible to fool.

However, I do not agree with the police Lt. who says GPS has a delay in the system caused by the satelite which invalidates it. The device on the car records your location and speed. That data is locked in place and transmitted to the satelite. The postal service is late delivering mail all the time, but that doesn't mean the letters you receive are inaccurate because they took a while to get to you.

>That data is locked in place and transmitted to the satelite.

Nothing is transmitted to satellites in a GPS system, everything in the car is passive. GPS units only receive, they don't transmit anything. If his parents were getting email when he went over 70 it was a separate system connected to the GPS radio, most likely via the cell phone network.

I think "traffic safety" is a euphemism for "municipal pork". I hope he beats the ticket.

Quote:

Originally Posted by Morpheus (Post 23560)

I think "traffic safety" is a euphemism for "municipal pork". I hope he beats the ticket.

Radar/Laser is more accurate than GPS when it comes to specific speed at a given moment (like being shot by radar) I hope he wins but I suspect he will loose for technical reasons.

Quote:

Originally Posted by rhertz (Post 23632)

Radar/Laser is more accurate than GPS when it comes to specific speed at a given moment (like being shot by radar) I hope he wins but I suspect he will loose for technical reasons.

I don't think we have laser in this area do we? Radar is not entirely accurate, though I do concede that it's probably more accurate than a GPS system available to a regular consumer.

No way, consumer grade GPS units are incredibly accurate, especially now that they don't have to worry about Selective Availability (thanks, Bill Clinton!).

Quote:

Originally Posted by joepole (Post 23767)

No way, consumer grade GPS units are incredibly accurate, especially now that they don't have to worry about Selective Availability (thanks, Bill Clinton!).

I thought they operated over averages. Like knowing the location at two points and knowing the time and distance between those points. I just didn't realize it was reponsive like a speedometer. My GPS unit is pretty old and the elevation readings are particularly useless.

Elevation is useless, but GPS units can use doppler shifts to detect speed changes not just location deltas.

Quote:

Originally Posted by joepole (Post 23775)

Elevation is useless, but GPS units can use doppler shifts to detect speed changes not just location deltas.

Pretty cool, thanks, that's good to know. My son is 14 and will be driving soon. I would like to get messaged if he crosses over 70mph.. :D