The Global Positioning System (GPS) is a constellation of 31 satellites which is used for navigation and precise geodetic position measurements. Data from over 2000 receivers have been analyzed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. JPL’s GipsyX software is used to produce these time series and other useful data products. Each site is represented by a green dot. The direction of horizontal motion away from each green dot is represented by a yellow line. The length of the yellow line indicates the rate of motion.