High-Precision Platform Positioning with a Single GPS Receiver

The goal of the research described in this paper is the design of a GPS data processing technique capable of producing high-precision positioning results, regardless of platform dynamics, utilising only a single, high-quality receiver. This is accomplished by combining two processing philosophies: point positioning – making use of precise GPS constellation ephemeris and clock offset information to estimation a single receiver’s state; and carrier-phase-filtered, pseudorange processing – supplementing pseudorange-based positioning with carrier-based position-change information. Results determined via developed software, indicate that near decimetre-level positioning accuracy is attainable for a variety of platforms ranging from static, terrestrial reference stations, to aircraft, to satellites. A number of modelling improvements can be applied to the existing software, and testing in the real-time environment is planned. INTRODUCTION A primary application of GPS is the precise positioning of a myriad of differing user platforms over a broad spectrum of environments, on and above the earth's surface. Current processing techniques rely on relative positioning between receivers, carrier phase ambiguity resolution, differential receiver corrections, or spatial interpolation of receiver network information, implemented in dynamics-tuned filtering schemes to greatly improve position accuracy over that provided by the Standard Positioning Service. The potential of point positioning is that it can remove these cumbersome aspects of GPS positioning for many applications. The authors have devised a novel approach which obviates the need for these techniques by using data from only the user receiver and products of the International GPS Service (IGS). This approach is not adversely affected by the decorrelation of biases in relative or differential positioning, un-resolved phase ambiguities, spatial interpolation errors, or assumptions regarding platform dynamics, and only requires the tacit assumption of sufficient GPS signals for positioning. In the following sections point positioning and pseudorange and carrier-phase processing are discussed. Then our single-receiver, platform-independent processing strategy is described. A number of tests with terrestrial, airborne, and spaceborne data are discussed, conclusions are given, and plans for future research are specified.