ScanGauge II Odometer off 3%, OEM Odometer off 1%

[Whaleya]

Using GPS to find the distance from point A to B (without moving) doesn't take elevation, etc into account. This is different from using the GPS while moving from point A to B, in which case it measures the real distance traveled.

[jmsolt]

Has anyone had problems with the display going plank?

[Pug]

Originally Posted by jmsolt

Has anyone had problems with the display going plank?

I don't remember the exact circumstances, but yes, it has happened twice.
I pushed a button, and the display came back with no loss of data.

[Webwader]

I haven't used the Scangauge with my GPS yet but I did notice that it is 3% slower than the RL odometer. I made the 3% adjustment for now and I will be leaving on a trip Thursday with the GPS on board.

[djdj]

Originally Posted by swampler

You sure about that? My GPS shows elevation, which makes it logical that elevation would be taken into account, otherwise it would be worthless.

When I say that, I mean it doesn't take into account the ups and downs. If you drive up 50 feet, then down 100 feet, then back up 50 feet, you have travelled a little farther than you would have if there were no elevation change at all, and yet your starting and ending elevation are the same.

[Nailing Malarkey]

Originally Posted by swampler

You sure about that? My GPS shows elevation, which makes it logical that elevation would be taken into account, otherwise it would be worthless.

Your GPS fixes your location in 3 dimensions. So up and down in the Gross sense are included in calculations of distance. The largest source of error is the measurement rate. Typically it might be 1 sample per second in a hand held. A car at 70 mph moves about 103 feet in one second. If that was anything but in a straight line the the value would be the cord length and not the arc length. In practical terms this error is very small for a car trip and can be ignored. Trust the GPS first.

[blconnection]

I work with GPS as a profession and could go on and on about GPS including several factors that can greatly reduce the accuracy of GPS height. I will spare you unless there is an interest.

My thought is to compair the speed estimate from GPS vs the Ridgeline speedo or ScanGauge. The point is that GPS does not directly measure speed but calculates it from positon measurements and elapsed time. Generally GPS will do the calculation every second (not alway true). GPS is almost always better than a millionth of a second (microsecond) in time accuracy so any error in postion will show up in speed errors.

With 102.66 feet in one second at 70MPH, 104.133 feet at 71MPH, 101.2 feet at 69MPH. So it is about 1.466 feet (17.6 inches) per mile per hour difference so speed will be very sensitive to distance errors. So sensitive I would bet that the GPS does some averaging on the speed readout to smooth the reading! My guess is that if they are smoothing the speed calculation they may also be averaging (smoothing) the overall distance calculation.

Anyway you may want to take a few minutes to look at the velocity (speed) as well when you run your test.