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From Fellrnr.com, Running tips
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{{:GPS Accuracy-summary}}
The values used are simply 10 minus the value for trueness and standard deviation. The overall is 10 minus the standard deviation from true values.
{{Alert|message='''GPS Accuracy Testing'''<br/>�New New versions of the firmware for the Garmin 620 and Fenix 2 are being tested.<br/>�Initial results indicate that GPS accuracy is significantly improved for the 620.}}
=Methodology=
''Main article: [[GPS Testing Methodology]]''
* Under normal conditions the GPS accuracy is quite good for most devices.
* The accuracy of a calibrated [[Footpod]] is far better than any GPS device. Without calibration the Footpod is more accurate than any watch currently on the market with the exception of the 310XT/910XT with a Footpod backing up the GPS.
* The Fenix 2, Garmin 620 and Garmin 10 are noticeably poorer than the other devices. I found the accuracy of the Fenix2/10/620 in general usage to be rather grim, and I did some testing pairing them up with the 610 or the 310XT. In all cases the Fenix2/10/620 would have poor accuracy compared with the 610 or 310XT on the same run. On one run, the 620 lost over a mile over a 28 mile distance. When Garmin replaced my 620, the new watch would lose 1.5 miles on a 20 mile run!
* The Fenix2 would repeated loose satellite reception, something I've not seen with any other watch. The statistics do not reflect just how bad the Fenix2 is, as some of the data is too bad to analyze.
* The results of the Garmin 610 & 620 indicate the problems with the 620 & 10 are not inherent in a smaller device. * The improvement in GPS accuracy of the 620 with updated firmware shows just how important the software can be. With the earlier firmware the 620 lost over a mile over a 20 mile run!
* The accuracy of all devices is better in a straight line than on curves or bendy routes. My course is a tough test for GPS devices with many curves and only a few relatively straight sections.
* Not surprisingly, accuracy drops going under the bridge.
=Recommendations=
Here are some recommendations for GPS watches.
* Most GPS watches are accurate enough for casual running. However, the Fenix2, 620 and 10 have such serious problems that I would not recommend them even for casual usage.
* The better devices are accurate enough for most runners if their limitations are understood.
* None of the devices were accurate enough for a runner to trust the display of current pace for training or race pacing.
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=Some Devices Are Better Than Others=
Below is a section of two runs showing the same section of the course, both taken at the same time, one from the Garmin 310XT and the other from the Garmin 620with the early firmware. These give a good indication of (With the accuracy problems I've seen with later firmware the tracks from the Garmin 620look like the 310XT. )
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=Garmin 620 Issues=
The Garmin 620 has become rather had some notorious for problems with its poor GPS qualityaccuracy. I raised The table below shows the issue changes with Garmin support and they kindly sent me a replacement device, but as you can see belowvarious firmware versions, culminating in the GPS-3.30 firmware that resolved the replacement is actually worse than my original unitissues. I've also broken down the readings by firmware version, and you can see including some slight improvement going from V2.90 to V3.00, but it's only slight. testing I also tested the 620 did without EPO data (NoEPO row below) and with a Footpod (+FP row below).
{{:GPS Accuracy-g620}}
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