Finally made it out to Folsom Lake for a fine day of sailing and GPS track collecting. Once I was back in the lab, I downloaded the track data with gpsbabel, and was ready to import the data into GRASS.
gpsbabel -t -i garmin -f /dev/ttyS0 -o gpx -F trip1.gpx
I was particularly interested in how fast we were able to get the boat going, however my GPS does not keep track of its speed in the track log. Also, I had forgotten to set GPS up for a constant time interval between track points. Dang. In order to compute a velocity between sequential points from the track log I would need to first do two things: 1) convert the geographic coordinates into projected coordinates, and 2) compute the associated time interval between points.