I uploaded my .gpx file to ka72.com, and although my 5x10 sec runs are around the mid-twenties, the 2 sec peak says 15.87 - which is what it shows in the Max column on the sessions page?

It also says my points are more than 2 seconds apart - can this be set on the GPS (Garmin Foretrex101) or is this just a result of the type of GPS?

Yes, there is something odd about your results. Another is that the best 10 second run is better than your best 100m (about 5 or 6 seconds).

I think from memory that the Foretrex 101 is only 'auto' trackpoint. This means it makes data points at seemingly random time intervals (there is a system but to us it appears random). If you can find a setting to make it record at 2 second intervals it would work far better.

Auto trackpoint intervals will severely hurt your recorded speeds (as you have discovered) so it is probably time to update the GPS to at least a Garmin Foretrex 201, but preferably a Locosys GT-11 (much better) or GT-31 (best). These last two GPS use the far more accurate 'Doppler' speed data at 1 second intervals.

I think I had a 101 (died years ago...and my memory ain't what it used to be) and you definitely could put it on 2 sec intervals, which you will have to do if you want to get any sense out of KA72 etc. It will record on track point so you will probably get an extra 1/2 knot on your 2 sec but the other measurents will be pretty much same as a Navi 31 doppler reading with the possible exception of the alpha.

Go to "track page",then "set up track", it gives you the options of DIST, TIME or Auto, choose TIME and put in 2 sec. The Dutchies used 2 seconds to try to reduce the spikes you get by using 1 second intervals when recording with a minimum grid pattern of about 2 metres in tracklog format.

Unless you intend to set records the Foretrex will do fine and the display is easier to read.

Thanks sail quick and yoyo - l remember setting this when I got the unit, will set it again and test out at sandy point on Saturday, looks like good wind (for me and my limited skills).

Hey Zeeber. Introduce yourself to me on Saturday or any other time you are at Sandy Point. This year I have numbers on my sails: AUS-20

Cheers, Andrew

Will do thanks Andrew.