Speed Accuracy

[kitch76]

I have a Navman iCN 330 and was wondering how accurate is the speedo read out in these types of GPS'

[Whatsthatbeeping]

I use my tomtom both in my work van and the Paj. In the work van the speedo will be saying 120 kph while the tomtom reads 100kph. In the Paj, the speedo reads 100kph as well as the tom tom.

I'm inclined to trust the reading of the Tomtom as I know that the Paj has oversized tyres, therefore the speedo would be reading at a lesser speed than what actual speed is. But taking into consideration that most speedos have a 10% (or so) error (on the overspeed side) I have sorta worked out that the speedo on the Paj is now reading actual speed and that the work vans speedo is over actual speed buy 15%.

So now I use the Tomtom as my speedo and it also explains why when I've go through a speed cameras at 125kph in a 110kph zone in the Kia van I haven't been pinged

Also I had one of the other guys from work riding with me and he brought along his Top spec Tomtom to check if there was any speed differences between the 2 and they were both dead on the same in the one vehicle.

[Marc 1]

I've got a Uniden GPS205 radio/GPS in one unit and despite it's cheapo price it seems to be pretty accurate - the Father in law's Garmin unit and mine read the same whilst we were in convoy and every time I pass under the speed check radar on the Hume near Wodonga it's within 1kph. I've noticed though that I often trip the speedwarning (set at 113kph) on steep inclines despite my speed remaining the same. I guess it adds evidence to the fact that altitude changes are not handled well by cheap GPS'

Hope that helps, Marc 1

[OFFTRACK2]

My Garmin seems to be very accurate, although the max speed it recorded is 762Km/h :D :D who says GQ Patrols are slow.

Apart from the odd glitch like that both it and my PDA running tom tom all seem to correspond ok and seem to match those temporary speed camera things (the one that tell you your speed rather than empty your wallet) they use at some roadworks

[Wombat]

I have a Shinco 350. In my wife's car it says what the speedo says, in my Maverick it's within 2-3 Km/H, but in my truck (Isuzu FRR500) Speedo read is out by 10% ie Speedo says 100Km/H Satnav says 90Km/H. So now I go by satnav.

[p38arover]

My Garmin seems to be very accurate, although the max speed it recorded is 762Kl/h :D :D who says GQ Patrols are slow.



kilolitres per hour? Man, that's pretty heavy fuel consumption.

Ron

[p38arover]

Odd that this thread has arisen.

I was wondering the same thing as I drove home tonight. I was checking my "new" Disco's speedo against the GPS. At 80km/h on the GPS, it is doing 85 indicated on the speedo.

I checked it on a straight section of road as I don't know how the GPS would indicate on winding roads.

I wonder if Nissan on Patrol and Fenring have ever tried their GPS against the calibrated speedos in their police cars? They must have - I know I would have just for my own benefit :)

C'mon guys, have you done so and how did they compare?

Ron

[ravofireman]

i have a umm i dunno what it is haha

It is 5 to 8 km out depend weatehr u are on the flat or on a hill hehe,,

[Davo1]

Seems some cars are different from others. New Falcons run at around 100 km/hr indicated but at 94-95 km/hr on GPS. confirmed withTom Tom & magellan.
My 100 series is accurate up to 80 km/hr but then reads at 100kms/hr = 96 on GPS.

Just finished working at the Clipsal 500 in the 2nd chase car - Commodore SV6 police pack (tried catching the lead pace car SS V8 & no dice!) - speedo was spot on with GPS at all speeds. So watch out for the police!!

[p38arover]

Our Forester when displaying an indicated 120km/h on the speedo is showing 110 on the GPS.

The speedo on my Rangie, with bigger tyres, reads slow - that's worse as it is easier to speed without realising it. I have to allow for that.

Ron

[westvictoriaHILUX]

I have a magellan gps315. Very simple but when im doing 100kmh it reads 108kmh. I believe the GPS of i have bigger tires on. The GPS seems to match up perfectly with da old mans VE SS Com so i must be accurate. Or very close

[timespast]

My Garmin seems to be very accurate, although the max speed it recorded is 762Km/h :D :D who says GQ Patrols are slow.



Heh mines been upto 934kph but that was on a 747 to the USA!