How accurate?

Question

how accurate are sat nav speed displays?

Answer 1

Normally the sat nav speed displays are pretty accurate, but not as accurate as a properly calibrated speedometer would be.  As long as your wheels aren't slipping, your tire size / inflation is correct, etc the speedo should be exact.  The sat nav has to update every so often, and if it's refreshing slowly it will only be an approximation of the speed you are driving.

It should be a relatively negligible difference, but if the refresh on the sat nav is a second or two and you are driving on curves, it will be off more then a straight road.  If you are off 4 mph you should check to make sure your speedo is calibrated properly.

Go on a straight stretch of freeway, and lock your cruise control at exactly 60 mph.  Don't change lanes or anything. As you pass a mile marker start your stopwatch, and stop the stopwatch as you pass the next mile marker.  It should be exactly 60 seconds...if it's off, go to a shop and have them recalibrate it.

Answer 2

I heard they r more accurate than your own speedo in the car

Answer 3

The speed seems to be fine on my Gar min 660...if your tires don't agree with you speedometer trust your Garmin...I do notice that I'm about 100 feet off on my GPS...

Answer 4

At least as accurate as the speedometer. My handheld GPS is accurate to 0.1 mph over a reasonable distance (after the first few paces).

Answer 5

I use a Garmin and it is right on the mark.....

Answer 6

very!!, i use a Tom Tom, its always accurate, when comparing to my speedometer, they read the same.

Answer 7

A car speedo is never that accurate, and there is a bigger margin allowed legally than you might think (10%). The sat-nav will be pretty near the true speed of the car.