Development and Testing of a Mobile Pseudolite Concept for Precise Positioning

Abstract

The concept of using a pseudolite (PL) in the reverse mode where the PL is positioned with respect to receivers deployed at known points is presented. In order to eliminate clock and other code and carrier phase biases, two types of double differencing approaches are described and analyzed, namely double differencing between two receivers (RX), one space vehicle (SV) and one fixed or mobile PL, and double differencing between two RX, one fixed PL and one mobile PL. The PL and GPS receiver modifications required to implement this concept are described. The results of an initial test conducted in a land vehicle at Holloman AFB, N.M., under the direction of the 746th Test Squadron are described. The test range consisted of a 600m course surrounded by six receivers deployed in a non-coplanar configuration at distances ranging from 1 OOm to 1,500m from the vehicle. The PL code and carrier phase data was used to assess its quality in terms of equipment noise, multipath, cycle slips, etc. The data was also analyzed in the position domain to assess the differential positioning performance of this augmented GPS system. Further development and testing plans are outlined, with emphasis on enhancing GPS-based testing capabilities at the 746th Test Squadron.