ncik,

In the second thread you refer to you have a polar plot from gpsar. Is that plot formed with data from multiple days or just from one track? (I don't know if multiple tracks are possible).

And if I would go out sailing 6 hours with a gps, would a plot indicate more or less the correct VMG? (if the main wind direction doesn't shift).
Would it be better to sail a normal racecourse for 6 hours or would it be better to just sail around all kinds of directions to measure VMG?

Regards,
Gill