coming from a GT31 I used the GW60 now for a few sessions. Other than the GT31 the top speed time displayed by the GW60 differs a lot from the times given for the same session in GPSAR. E.g. while the GW60 displayed a top speed of 46.00, GPSAR shows (doppler enabled) 44.93. I never had such big differences with the GT31. Any idea why that might be?

Thanks! Norbert

Norbert, the GW60 displays a max speed for 0.2 seconds, the GT31 for 1 second. The top speed for 0.2 seconds will generally be higher, which explains some of the difference - but not all. The GT31 data are also filtered, while the GW60 data are comparatively unfiltered; the GW60 data often have random errors of 0.5 knots, sometimes higher. So it's quite normal to see GW60 max speeds be 1 knot or more higher than the GT31 speeds. With the current firmware, you can change that by using speed genie, and just showing the top 1 or 2 second speed.

However, if you swim a lot (or clear the fin of weed a lot underwater), then you may get much larger differences from artifacts. The watch is more likely to loose reception under water (partly because the wrist tends to be deeper in the water), and it sometimes produces artifacts with high bogus speeds when regaining reception. GPSResults filters those artifacts out, and  the authors of GPS Action Replay and are working on updates to do the same. There's a lot of detail about this at

Great explanation - thanks a lot! Maybe another firmware update of the GW60 might help as well...