With a smart recording in normal GPS mode, the GPS system is continually active, so there's no loss in accuracy. The Fenix2 would repeated loose satellite reception, something I've not seen (the M400 has done this once). After using the gpsmap 62 for a few years - endless problems with the triaxial compass needing recalibration or not working at all. Often GPS measurements of races, especially marathons record a longer distance than the race. As you can see, accuracy suffers on curves, but is fine on the straights. (With the later firmware the tracks from the 620 look like the 310XT. When Suunto added support for the Galileo positioning system to Suunto 9 I was eager to test the GPS accuracy in GPS + Galileo mode. To make this device even more responsive, the manufacturer has added the WAAS program, GPS, and GLONASS capability to ensure that it maintains a precise GPS tracking capability whenever you enter your coordinates. Because it does not rain that frequently where I test, this has created some potential bias in my testing so I now ignore measurements taken during the rain. My thought is that enabling both GPS and GLONASS will increase the number of satellites above the horizon, and a modern chipset can have over 50 channels. In my discussions with engineers working on GPS systems, this type of smoothing is often performed with aKalman filter. There was some question last time as to whether our track was a metric, 400m track or a quarter-mile track. While it's tempting to take the various GPS watches on a single run and simply compare the totals, this is a flawed approach. While the L2 signal is considered to be the most powerful and accurate frequency, the civilian L1 is usually weak and altered, making it impossible for it to send accurate readings. I would expect there would be more satellites available with GLONASS enabled, which would result in the watch selecting the subset with the strongest signal that are more likely to have a narrow angle of separation, which would result in increased Dilution of the Precision. The Suunto Spartan Ultra seems to do particularly poorly with GLONASS enabled. I've talked to a GPS specialist who tells me that they have seen this in GPS systems they've tested (though not necessarily consumer grade systems.) The results of the Garmin 610 & 620 indicate the problems with the 10 are not inherent in a smaller device. With the accurate WAAS-enabled GPS receiver, explorers can get accurate location information while still taking advantage of the 24K maps provided by the TOPO map downloader. In practical terms, I've found that I always have to use a Footpod to pace a marathon or for critical speedwork. This is why I've accumulated a lot of data to do a statistical analysis to work out which is really better. It's a bit like evaluating an athlete's ability on the basis of one event; everyone has good days and bad days, and that applies to GPS watches as well. Continuing the theme of poor accuracy with GLONASS enabled, the Garmin Fenix 5X demonstrates even worse performance than its peers. I have no definitive explanation for this, and I do have a working hypothesis. It’s fairly hard to get GPS accuracy below 5m, indeed the precision of GPS is 5m, and hence working out how fast you are going and exactly where you are is difficult. Trail running tends to be rather harder for a watch to measure accurately. Accuracy of iphone locations: A comparison of a) assisted gps, b) wifi and c) cellular positioning. kofiwidget2.init('Support Fellrnr on Ko-fi', '#29abe0', 'K3K41J393');kofiwidget2.draw(); I evaluated the real-world accuracy of GPS watches while running over 12,000 miles/19,000Km and recording over 50,000 data points as part of my evaluation of the Best Running Watches. Garmin devices are set to 'smart recording'. To view the current accuracy rating of your device, refer to its Satellite Information Page . Transactions in GIS, 13, 5–25. With the earlier firmware the 620 lost over a mile over a 20 mile run! The difference between completely clear and fully overcast is generally less than 0.1% and my testing includes a similar mix of cloud cover for each watch, so I ignore this difference. Levels of Differential GPS Accuracy The "Standard DGPS" belongs to the first generation of equipment used in large volume. 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