Anyone with a Commander that has checked their GPS accuracy?
I beleive that the GPS that came with my Commander shows 2% too low speed.
Alfred
GPS isn't perfect either, they dont handle change in altitude very well either. So if you're travelling down a steep hill at 110kmh it will see you moving forward slightly less than that. I'd still go with the GPS over a speedo any day though
I should have explained that I didn't compare the Commander GPS with the speedo, I compared it with an other GPS which I had earlier compared to the speedo in an other car that I verified against a couple of radar speed checks with displays.
I agree you can't trust the GPS speed travelling up or down a hill and it doesn't have to be steep to show a incorrect value.
The GPS speed is a horizontal speed so it doesn't take into account any changes in elevation. I suppose if you are a maths freak and can remember all that stuff from school you could work it out but ...... That said GPS have about a 1% error rate depending on how many sat's it is tracking (more the better and less error). The speedo only needs to have a 10% accuracy (to meed current legislation) so I would take the GPS any day. If you are interested there is an article in 4x4 Australia about GPS.
I finally found an explanation why the SATNAV was showing 2% low speed.
The speed shown on the SATNAV is NOT a GPS calculated speed, it is from the car's speed sensor. I found out when the SATNAV got the time stuffed and refused to find any satellites and this had no effect on the speed displayed on the SATNAV.
I verified against a couple of radar speed checks with displays.
I'd trust those even less than the Jeep's speedo! I've driven past the one near Geelong three days in a row, same car, same speed and got 3 different readings!
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GPS Speed error
