TRUTH TRAJECTORY ESTIMATION FOR GLOBAL POSITIONING SYSTEM USER EQUIPMENT TESTS

Abstract

Testing of NAVSTAR Global Positioning System (GPS) user equipment at the U.S. Amy Proving Ground (YPG) requires accurate position and velocity information. GPS position accuracy is 15 meters spherical error probable and velocity accuracy is .1m/sec RMS per axis. Proper evaluation of GPS user equipment requires position and velocity information more accurate than the equipment under test. YPG users laser trackers to develop a real-time estimate (RTE) of the trajectory. Independent analyses show that the RTE accuracy is about 3m and that velocity accuracy is about .25/m sec overall. This paper describes the development of the RTE starting from the raw laser measurements to the calculation of position and velocity in a local coordinate frame. Included is a description of the filter. The paper also discusses the methods used to verify the accuracy of the RTE.