Position location with the NBS/GPS time transfer system

The NSB/GPS time transfer system is a low-cost receiver of the GPS C/A code for comparing time standards around the world for time and frequency coordination. In order to achieve the highest accuracy for time and frequency transfer the local user must know the coordinates of the receiver antenna within the GPS coordinate system. For this purpose, a fully automatic position location program is included in the receiver software. The receiver performance for absolute differential positioning was evaluated in experiments over three baselines: short (26 m - 77 m), medium (131 km), and long (240 km). Solutions from the receiver were compared with WGS-72 first order survey points. Absolute positioning error varied from 4.1 m to 10.2 m. A 7.2 m mean absolute positioning error is found over eight separate results in the four experiments. The short and medium baseline differential positioning error varied from 1.2 m to 2.5 m, reflecting a limitation due to multipath delays.