Hi

Sat I sailed and ended the session but didn't not upload

Sun I sailed and thought the GPS might realize with 'time stamps'?? that it was a new session.

Sunday night I uploaded to Ka72 and noticed only 1 file on watch?

It downloaded only sats session.

qu.1 should I just download after each day? or did I do something wrong?


cheers guys

The GW60 only sees one file, and yes it is all time stamped. But unlike the GT31 the watch doesn't start a new file every time you turn it on. I was under the impression that KA72 can split the sessions, but I've no idea how to do it.
Certainly GPSAR and GPSResults will do it for you. I'm not sure about GPSspeedreader, Peter is improving it all the time, and splitting sessions was on his todo list. I'll download your file and have a look.

Hmm not sure I've found your file, there's one there for Shane on Saturday, but it hasn't any tracks for Sunday. If that's not you, can you help me find it?

Edit, a bit of sleuthing tells me you aren't Shane but Peter, and I still can't find a KA72 file for you. And just a Sunday post but no Saturday. So if you want to post the file to me, just PM me and I'll give you me real email address

I just uploaded a new version of GPS Speedreader that supports multiple sessions in one file (you get to choose which session to analyze, so you have to open the file several times in a row to analyze several sessions).

This version also has new functions to delete filtered points (which I need for a better display of sessions with artifacts, which are very common in foiling), and to delete a selection (for artifacts that make it through filters - rare but can happen). There's also the beginnings of jibe analysis in this version, which shows the jibes with the best minimum speed in the results table, and a percentage score (min. speed / max. speed within 50 meters before the turn center). That part is experimental, and will likely change in the future. Might still be useful for anyone working on jibes or alphas. At this point, it does not differentiate between jibes and tacks, but tacks usually have a lower minimum speed.

Thanks again peter, I'll download it now.

I had trouble with gybe analysis because I was looking in the wrong spot.

But I found it here. Right under the Distance result.

The Speed column is min gybe speed, the 5 results are ordered by highest first. the +/- column is your "score" the percentage of min speed to speed 50m back from turn centre.

I'm still not convinced this is an indication of the best gybe for alphas, but it's probably a good indication of the best gybe for hours and distance, when there's not the 50m separation to contend with


You can see here, my best alpha is at 15:24:23, but the best gybe is at 15:26:18, this corresponds to my second best alpha, a whole kt slower

Jibe analysis is intended for windsurfers who work on their jibes. It's objective feedback for measuring improvements. If you improve your jibes, your alphas should also improve. It may be more useful to anyone just learning to plane through jibes than to someone who'd been doing that for decades . With GPSAR, I'd say that scores in the low 40s deserve improvement .. but Speedreader calculates the score differently, using the max speed instead of the speed exactly 50 m from the turn center. With a nice speed gain as you start turning, as you have in this example, GPSAR would probably give you a higher score.

Whether the highest-scoring jibe is also best for alphas is a different question. As mentioned many times before, an alpha may benefit from a tighter turn, which in turn may mean loosing more speed. Mixing jibe analysis and alpha analysis would need more data, like the widths of the jibe. Would have done it but it's too windy here - we had to windsurf every day for a week now .

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boardsurfr said..
>>>>> Mixing jibe analysis and alpha analysis would need more data, like the widths of the jibe. Would have done it but it's too windy here - we had to windsurf every day for a week now .

Ah well, lucky you, you're on the right side of the globe right now, it's total wind drought here. Although the forecast is teasing us again.

OK, I agree it's a good measure of gybe efficiency, but does board width also come into the mix?
I'm thinking it's easier to keep speed up on a wider board?
Certainly water state is a huge factor. So if we're keeping records of how well we're progressing, we should take note of these parameters.

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decrepit said..
Certainly water state is a huge factor. So if we're keeping records of how well we're progressing, we should take note of these parameters.

Certainly, keeping speed when jibing in flat water is easier than when jibing in chop. But I have had both my top score and my best minimum speed in swell, with some lucky timing and a big push during the foot and sail switch period. That helped me to get 15 knots and above 70% - on flat water, I struggle to keep more than 12 knots or 60%.

years ago I thought I could get my best alpha out here gybing on a wave as it came through the gap in the reef. I did this all the time on my wave gear, but figured that wouldn't be fast enough. So took the speed gear out, it was then I realised how well speed gear didn't turn. I couldn't complete the turn on the wave face, Just went flying off the top, and landed very ungracefully on the other side.

I did experiment with starting the turn earlier, but somehow the alphas never ended up being any better than on flat water.