VMG - velocity made good towards a waypoint. That will tell you whether
pinching (and slowing) or freeing (for speed) will get you to the windward
mark quicker, or exactly what course on a downwind gybe gets you to the lee
mark quickest. You will need a 'relative bearing' (angle off the bow, or
pelorus) device to tell you when to tack or gybe onto the equivalent course
for the mark. You will need to get all the marks as waypoints, so this may
mean visiting each mark and entering the waypoint before the start.

If you can link the GPS to boat speed and direction then it can calculate
tide set and rate, or you can do it manually if they can't be electronically
connected.

The other useful feature is to be able to save the course sailed for later
analysis, but general purpose GPS software doesn't usually provide decent
analysis tools, so you may have to write your own. You should be able to
replay the whole race or selected parts, identifying where you gained or
lost ground and perhaps working out why.
--
Jeff Richards

"Amanda" wrote in message
...
Hi

I have the opportunity to crew on a racing yacht as tactitician and
would like to learn more about racing with a GPS. Apart from the
obvious (distance and bearing to the next mark) what other uses can a
GPS be put to in yacht racing?

I've raced dinghies and cruised yachts so I'm familiar with general
tactics and how to use GPS, but I need to put the two together.

Thanks for any help.

A.