Surfing for GPS

peteriegelRCMBB Founder

I’ve been surfing in an attempt to find out what GPS-for-runners manufacturers have to say about their accuracy in measuring distance covered. Here are some random findings:

1) The readouts of distance I’ve seen typically read to two decimal places. This would be 52.8 feet in one mile or 10 meters in one kilometer.
2) Some claim 95 to 99 percent accuracy (264 to 52.8 feet per mile, 50 to 10 meters in one kilometer.
3) One article mentioned that local interference affects accuracy, and for best operation one should use the units “under a big sky.” I assume that the claimed accuracy is obtained under unobstructed conditions.

Given the above it would seem that the runners who are disturbed about the supposedly inaccurate courses have not read the material that, hopefully, came with the unit they are using.

11/9/065:45 AM

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alanjonesMember

Just to back up what Pete has found, the study done in Australia comparing Differential GPS with the Jones-Oerth Counter, had problems when the course ran underneath trees. They showed a map of the course as GPS thought it went compared to where the road really is. Where there were trees, there was often quite a deviation. And, remember this is Differential GPS which is much more accurate than the normal, off-the-shelf, GPS.

Alan Jones

11/9/067:27 AM

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pauladamsMember

Another thing many people do not realize is that ones own body will block the signal. You can observe this by holding your hand over the GPS. So, the acccuracy is affected by where the device is mounted on ones body. A wrist mounted device is often less accurate than one that mounts on the upper arm. If the device is on the body side of the wrist it will be less accurate than if it is on the outside.

11/9/069:34 AM

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