Police cop backlash over GPS speedometer inaccuracy claim

The Luddite view of the police (who probably just want to keep things simple), has been comprehensively crushed:

The maker of a vehicle GPS navigation system is taking police to task over comments suggesting the units are unreliable.

Last week, a police spokesman said readings from GPS devices were not accepted as a reliable means of accurately proving a driver’s speed and therefore could not be used to disprove a speeding fine.

Software used by manufacturers was based only on straight-line driving, police said, and was less reliable because of signal loss through buildings, terrain or weather conditions.

Yesterday, former Navman engineer and current New Zealand development manager Sajeewa Dayaratne said GPS devices were susceptible to some interference but that was unlikely in New Zealand.

“The open roads in New Zealand where there are no tall buildings, and drivers are not frequently stopping, are perfect conditions for GPS speed readings.”

GPS speed readings are going to be more accurate than those on the car’s odometer.  Which is the problem really, as people with true knowledge of their speed are  likely to “speed” close to the limit.  

Automotive specialists last week swore by the accuracy of GPS devices for indicating speed.

Goodyear Timaru owner Carl Vaughan said using a GPS was the only way to get an accurate speed reading.

Dayaratne backed the accuracy of GPS units.

“If your GPS is receiving a signal from even just four satellites, current research shows dedicated GPS navigators have an accuracy of 0.2kmh. This is much more accurate than a car speedometer.”

Last week a Timaru driver approached The Timaru Herald after being told by police that his GPS reading, which showed he was travelling under the speed limit, would not be accepted.

Police said GPS devices were not recognised by or calibrated to the same accredited standards as speed guns and therefore were not a reliable means of gauging speed.

However, Dayaratne said GPS devices worked off a mathematical formula and did not need calibrating.

There is some lag, where you can accallerate or decellerate and the speed reading takes a few seconds to catch up.  But when you’re in the process of driving and you get clocked at going at X km/h, you can’t be certain your GPS will have you are that speed.

And this is why you need at least some tolerance.  It will be a complete waste of court and police time for people to argue over 1 or  km/h based on the radar gun reading being at 101 km/h, and your GPS saying you were at 100.


– The Timaru Herald

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As much at home writing editorials as being the subject of them, Cam has won awards, including the Canon Media Award for his work on the Len Brown/Bevan Chuang story. When he’s not creating the news, he tends to be in it, with protagonists using the courts, media and social media to deliver financial as well as death threats.

They say that news is something that someone, somewhere, wants kept quiet. Cam Slater doesn’t do quiet and, as a result, he is a polarising, controversial but highly effective journalist who takes no prisoners.

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