GPSAR Pro 4.18 has a check box for doppler and trap in the speed results view. I had doppler on and trap was only changing a few speeds by a few hundreths, so I had it turned off. Also given the 2sec and 10sec numbers are so close, they may of fixed the 1/2/3 second prob?

GPSresults V6 also has a check box for doppler and interpolation. I didn't add it to the comparison as it wouldn't recognise my alphas or NMs. Also buggered if I could see where to get total distance from!

My tracks are the extreme for spending lots of time in the water and the error will get smaller if you are usually above your minspeed and the minspeed is not set too high. So back to Pauls original question, best comparisons / results are usually made if you have all the data, so I'd recommend having minspeed off for memory card (1 gig card will have stacks of room!). Then if you usually sail for more than 5 hours straight, I'd set minspeed on the data logger to 2 or 3 knots and only use it as a backup to the SBN file. Also you can always filter it later to remove low speeds.

Am I understanding your post correctly - so for the 11 minutes under 3 knots, GPSAR gave an average speed of 0.64 knots for the SBN file and 1.12 knots for the SBP file? If so I wonder how it calculates a speed when it has no data! Either way it does sound like your results are slightly different, but more accurate than what I'm getting out of realspeed!

Hi Scott,
yes you understand correctly....I wondered if the slow rise and fall of the data trace which I mentioned gives rise to the 0.64kt average even with the min speed set at 'off'.
Yes, it is a cool program. Yann Mathet, the program author, has a very good forum and info service and he could answer many of your queries, I'm sure.
You do need to set doppler, trapezoidal and cubic on the results page, (which also gives distance covered).
Have a look at the analysis of gybes and tacks under speed results...very nice for a slalom sailor.......also the way you can click and scroll any section of the track to see average speed, distance covered etc