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# GPS moving average speed

732grl
0 Points

I need to find a GPS that will measure moving average to the tenth of a mile per hour at speeds in excess of 100mph. Most consumer units display 3 digits so at over 100mph accuracy is limited to 1 mph. Any suggestions??

## Comments

Now consider a speed of 100.1 miles per hour: 100.1 x 5280 / 36000 = 146.8 feet in a second.

Also consider a speed of 101 miles per hour: 101 x 5280 / 3600 = 148.1 feet.

Consumer GPS devices are only accurate to between 10 to 16 feet under ideal conditions. So the error between two position fixes could be anywhere from 20 to 32 feet. And the GPS uses those positions to calculate speed.

So for accurate readings of 1/10 mph at 100 mph you would need gps accuracy of about 0.1 feet and for readings that are accurate to 1 mph you would need GPS accuracy of 1.3 feet. No way that you will get this from any consumer grade device. I wouldn't even trust readings to the nearest whole mph.

I did a review of the Garmin GLO bluetooth GPS receiver for GPSTracklog last year. This unit is somewhat unique in that it takes 10 position fixes per second instead of only one per second. It is not a standalone device however, just a receiver that sends data over bluetooth. You need either a laptop computer or a compatible Android/iOS devices to process that data. And your app must be capable of actually reading 10 fixes per second (older software typically is not).

Garmin positions this device for aviation use at high speeds where 1 fix per second is a bit slow. However, I did some extensive testing and don't feel that the GLO is any more accurate than other consumer devices in real world use. So the higher sample rate doesn't necessarily translate into better quality data.