There are a couple of flight analysis software available for cross-country soaring, most of which can download trajectories from Garmin GPS.
The commercial ones I am sure of are :
SeeYou,
StrePla and
CouTraCi. The last one is simpler (and cheaper).
Paul Remde's
Soaring links offers a couple of links.
Some
Googling might help too.
If you want something free, you might use two different codes, one to download the flight from the GPS, and possibly to convert it to the widespread IGC format, and one to view it.