Accuracy of GPS Speed indicators

MrRee4U · Posted: Wed Jun 15, 2005 9:15 pm Post subject: Accuracy of GPS Speed indicators

I have just purchased the Medion MD95900 unit, maps by navman.

What I wondered could anyone / would anyone care to comment on the likely accuracy of the speed indicator when in use locked onto 6 - 9 sats.

What are anyones thoughts, good bad, accurate +/- 10% or what

Cheers

A Question

Oldboy · Posted: Wed Jun 15, 2005 9:36 pm Post subject:

I've seen a figure of 0.3% quoted somewhere.
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Pocketgps · Posted: Thu Jun 16, 2005 2:35 am Post subject:

You need a level and stright road and a constant speed to get the best accuracy.

StevenGourlay · Posted: Mon Jun 27, 2005 8:53 am Post subject:

they are accurate you will see that they give you a lower speed than what your card indicates but this is due to cars set normally 5mph greater.
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hertz · Occasional Visitor Joined: Apr 01, 2005 Posts: 9

I have discovered that they vary with different cars. My Peugeot 306's speedo is spot on, but as Steven Gourlay says, many cars speedos read up to 5mph faster than actual speed. My Freelander (previous one and present one) both indicate that the speedo is 5mph faster than my TomTom shows, and a Nissan Micra I once borrowed was also 5mph ambitious. At least, it reduces the chance of getting your photo taken!

Skippy

mburton2 · Posted: Thu Jul 14, 2005 7:39 am Post subject:

Mine seems to vary....

When I was using my old Navman/Smart ST, it was reading APPROX 10mph lower than the speedo at an indicated 75mph

My current Globalsat BT338/TT5 is much closer to the speedo on the (same) car.......about 5mph less than the Navman woudl read.

The Legal requirement for a (OEM) cars speed accuracy is:
+10%+4kph

ie its POSSIBLE to indicate 114kph, but only be doing 100kph

gtvv6 · Occasional Visitor Joined: Jul 13, 2005 Posts: 19

Thing is, car speedo accuracy may not be uniform accross the scale, my Alfa shows +4mph at 70, but at 30 it's spot on, so don't assume you can drive at 35mph speedo reading safely in a 30 zone.

I borrowed my son's Garmin Vista a while ago when I went away for a weekend, he has since accused me of doing some obscene speed as shown in the trip computer (which I forgot to clear), he isn't buying my story about poor GPS accuracy! He takes my lectures on safe driving with a huge pinch of salt now Embarassed

mburton2 · Posted: Sat Jul 16, 2005 10:12 am Post subject:

Yip you are right, the accuracy CAN vary depending on you actual speed, what I quoted was the MAX in-accuracy allowed.

Donald

Skippy · Posted: Fri Jul 22, 2005 9:43 pm Post subject:

GaryC · Occasional Visitor Joined: Jul 12, 2005 Posts: 17

With my speedo reading 30 the SatNav reads consistently 27mph and at 70 straight and level only 64mph by GPS
If GPS is as accurate as said and given I solely bought the SatNav to keep me on the straight and narrow as far as speed and speed cameras are concerned, it came as quite a surprise to find according to GPS it's unlikely I have exceed a speed limit by more than the 'allowed' 10% at the most...I better find another use for it or what a waste of money Crying or Very sad

The one thing that worries me is if I am travelling in a convoy though a 30 limit, my speedo is reading 30. Question is then is GPS so accurate especially in built up area, or is everyones speedo set accurately 10% fast!?

Oldboy · Posted: Fri Aug 19, 2005 10:43 pm Post subject:

Pocketgps · Posted: Sat Aug 20, 2005 12:52 am Post subject:

GaryC · Occasional Visitor Joined: Jul 12, 2005 Posts: 17

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