Global Positioning System Sensitivity Experiment

Abstract : This experiment demonstrated the obtainable accuracy for estimating changes in a receiver antenna position using Doppler techniques and the NAVSTAR Global Positioning System (GPS). The antenna was periodically moved to three locations approximately 2 to 3 meters apart. The moves occurred within a one minute Doppler count interval every fifteenth interval until at least six Doppler measurements were made for each location change. These measurements were used to determine the observed change in range from the antenna to the GPS satellite due only to the movement of the antenna. The calculated change in range was computed from the surveyed distance moved and the angular differences in elevation and azimuth between the direction of the move and the direction of the satellite. The observed and calculated changes in range were compared. The three-dimensional antenna position changes were estimated using six observed change in range measurements for each location change. The estimated results were compared with surveyed values and demonstrated subdecimeter accuracy. (Author)