NAVMAN SPEED ACCURACY

Getalife · Occasional Visitor Joined: Feb 26, 2006 Posts: 2

The vehicle I have the Navman in at the moment is always showing 5mph slower than the vehicle speedo, which I thought was quite accurate.
A vehicle I have just rebuilt has had the diff ratio changed and the speedo is not showing the true MPH. I want to use the NAVMAN speed function till the vehicle speedo is calibrated. Any views on how accurate the SATNAV reading is please.

mikealder · Posted: Sat Mar 25, 2006 11:33 pm Post subject:

The GPS unit should be more accurate than any fitted speedo, this only applies when in a straight line and flat road - it is quite normal for the vehicle speedo to read a higher value than the one reported by the GPS, this could be down to the diff ratio (if messed with) and or tyre/ wheel size will further compound the problem, use the GPS speed and you will be OK, but if your speedo is out by a considerable margin you might want to consider getting it re-calibrated - Mike

Skippy · Posted: Sun Mar 26, 2006 1:04 pm Post subject: Re: NAVMAN SPEED ACCURACY

dk · Occasional Visitor Joined: Mar 11, 2006 Posts: 12

Yes my Navman shows my speedo is 5mph over, it does on my friends car and my good lady`s car.So is it a coincidence our cars read 5mph out?
or is it the Navman?

TerryWalsh · Posted: Wed Apr 05, 2006 8:43 am Post subject:

Just about all car speedos show something like 5 MPH over. I think the manufacturers deleiberately err on the side of safety. I have a US built Focus ZX3 which I brought back to UK with me and its speedometer is always within 1 mph of the Navman display, but when I use the Navman in my wifes car and in several other cars their speedos always overread by 5 or more mph. In fact at 70 indicated in my wifes car the Navman only shows about 63 mph.

ohreally · Occasional Visitor Joined: Oct 30, 2005 Posts: 10

As a couple of posters have already alluded, the speedometer must not display a true speed which is less than actual speed thus munufacturers calibrate to show faster than true.They're are parameters they must operate within though and it will rarely be more than 3-4 mph over (though never under).

anglefire · Posted: Mon May 01, 2006 7:33 pm Post subject:

My previous 2 cars (Both Audi's) read about 10% higher than the GPS indicated speed. Both my OriginB2 and 630 read the same within update time.

My current Audi reads about 4% higher than the GPS.

As I understand (And could easily be wrong!) the tollerance is 0% low 15% high. Ie can indicate faster than true but not slower. Between 3 and 10% seems typical.
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MoPlain · Occasional Visitor Joined: Mar 04, 2006 Posts: 53

I have the Navman ICN650 self contained unit and TomTom 3 and 5 on a PDA. The PDA can use one of three GPS receivers I have. If I am using both sat nav systems side by side both indicate the same speeds (and 98% of the time distances to next turns etc.). I use them in two different cars and the cars always read about 4-5 mph faster.

123381 · Occasional Visitor Joined: May 06, 2006 Posts: 5

my mitsubishi shogun sport is only 1mph out

Regards

Puddy

zzf00l · Regular Visitor Joined: Jul 17, 2006 Posts: 84

I believe the legal requirement for speedometer accuracy is +/- 10mph

Skippy · Posted: Fri Feb 09, 2007 10:41 am Post subject:

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