Just got myself a Garmin Nuvii50 GPS and according to that when my speedometer reads 100k/ph I'm only doing 90k/ph so I'm guessing that the Speedometer is not reading correctly and that the GPS is reporting my speed accurately. Am I right!
gedo1,
Jun 24, 6:57am
If you want to check for speedo accuracy by comparing with the reading from a GPS, try to do it on a long stretch of straight road. This gives a track that is more accurate than one on a road with many turns.Cheers
morrisman1,
Jun 24, 6:59am
I would trust your GPS more than the speedo but as said, GPS speed should only be fully trusted when driving in a straight line
msigg,
Jun 24, 7:00am
you might be, has your car got smaller wheels, most speedo's are 2-6km higher reading than actual, this difference you have seems to be a bit high to me. I suggest you keep your eyes on the road not on the gps.
smac,
Jun 24, 7:03am
GPS does definitely have gliches in corners - was sitting on 95 going into a corner last week just out of Taupo, would have slowed through the corner, and GPS shot up to 100 then 122 as I exited corner before coming back to low 90's again. Weird.
kiwikidd77,
Jun 24, 7:08am
I only glance at the GPS every 20 minutes or so. I much prefer to concentrate on the road. The checking I did was with a friend driving and me keeping tabs on the GPS.
net_oz,
Jun 24, 7:29am
Passed some vehicles a few weeks back on a straight stretch downhill road. My Garmin read 130 in the round dial while the maximum speed showed 171. Speedo was showing 135. Go figure.
slarty45,
Jun 24, 8:00am
My car speedo reads 5km high compared to GPS. GPS matches exactly roadside radar speed indicators that are placed at entry to some towns.
neville48,
Jun 24, 8:21am
so try doing 110kms and then say to the officer that gets you for speeding ."but officer, my Garmin says etc etc etc" thats when you will have yur answer.
slarty45,
Jun 24, 8:26am
And he will say the digital GPS is not as accurate as his digital radar, yet GPS good enough to guide missiles to a metre or two.
and before anyone goes down the 'military grade GPS' track, US of A changed it in 2005 I think it was, from what they called Selective Availablility to Selective Deniability. Essentially that means everyone gets the high precision signal unless the states have security concerns, eg war zone, in which case they will degrade the signal quality drastically or even disable it.
Prior to 2005 there was civilian GPS and military GPS, the difference between them being the military signal included correction for ionospheric interference
socram,
Jun 24, 10:22pm
Just returned from the UK where if the motorway roadworks signs are posted at 50mph, you'd better not exceed it. (They have cameras at many road works sites.)ALL traffic was travelling at exactly 50mph, obviously controlled by those using GPS. Ours said exactly 50mph too.
Off topic, but if the TomTom says the current speed limit is 60mph on the open (UK) country roads, just check, as they are often out of date and the limit may well have been revised and signed at 50mph.
ken171,
Jun 24, 10:35pm
GPS Units are 1% plus/minus of true reading.
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