It does all seem to be flight based that's for sure. But can you define your parameters a bit better, when you say navigate via gps do you mean move from known starting point to a known waypoint ? Or from a known start point to a waypoint that is identified by a system other than gps coordinates ?
If it is the 1st option try this link http://letsmakerobots.com/node/19554 you may have found it already but there is some useful info there.