GPS Powerpoint: Day 1: to watch / to download
GPS Powerpoint: Day 2: to watch / to download

Videos:

How GPS works : click here
Introduction to Geocaching: click here
Launchpad_ How GPS Works : click here
The Geocaching Documentary: click here
Geocaching Class - Learning Geocaching in School : click here
Geocaching how-to.: click here
GPS Principles Video.: click here