GPS Navigation: Combining Pseudorange with Continuous Carrier Phase Using a Kalman Filter

The notion of aiding GPS code-ranging information with carrier phase measurements has been around for quite some time. The integration of these two complementary forms of data can provide highly precise position solutions corrupted by very little high-frequency error, which is advantageous particularly for high-dynamical situations. This paper presents two schemes, based on the Kalman filter, for integrating GPS code and carrier measurements efficiently. One of these schemes involves a general combination of the two types of measurements, where the vehicle motion is described as a random process. In the other, the continuous carrier phase measurements provide a dynamically exact reference trajectory in much the same manner as in an inertial system, and the pseudorange data is then used to update this reference trajectory via a Kalman filter. This method of integration looks especially attractive as a means of achieving good dynamical response while still retaining the benefits of filtering the pseudorange data.