just thought id mention that i took the gt31 for a jump.
the read out says 146.13 kn max horizontal speed (result of wing suit flying, although i did have approx 30 kn tail wind).
these little gps are great.
does anyone know how to do a 3d map overlay for the track?

Wow sounds awesome, chat to JN1 from SA he has designed a program to track windsurfers racing on a 3D course, may just work for you :-)

he called it sail play

www.seabreeze.com.au/forums/Windsurfing/General/Sailplay-port-to-Windows-Who-is-keen/

Nice one Cory, how does the altitude data look?

GPSarPro has an "altigraph" it will show speed and height at any point on your tracks. And does a replay of all 3.
Not a 3d GE overlay, but it may give you some idea of what is going on.
Note I'm at -30m on the estuary, so it's not that accurate.

awesome.
thanks guys.
theres a heap of fliers looking for something to use for performance improvement so if anyone wants to design something id say theres a fair market for it.