Global Positioning System (GPS) is a technology that uses the position of satellites to determine locations on earth. Technology has emerged that interferes with GPS.
Homemade GPS jammers raise concerns
January 17, 2003 article from ComputerWorld on the use of homemade GPS jammers.
GPS Jamming in a Laboratory Environment (PDF)
Article by Gregory D. Rash of the Naval Air Warfare Center Weapons Division (NAWCWPNS)/China Lake. Per the abstract: This paper identifies and discusses issues related to implementing a GPS jamming system in a laboratory test environment show how errors in measuring the amplitude of GPS jamming relate to the overall accuracy of the test.