There was no road for Production Vehicles to travel on in order to reach the waterfall location seen in the opening of the film. The crew had to hike the equipment a mile through the forest to the waterfall.
The last in a series of ATV stunts seen in the movie involves a dangerous, accidental crash that made the final cut of the movie. Fortunately, no stunt people were seriously hurt in the accident.
G.P.S. stands for Global Positioning System and invented by scientist - physicist Roger Easton, along with Ivan A. Getting (18th January, 1912 - 11th October, 2003) and Bradford Parkinson (16th February, 1935).