Range Filtering for Sequential GPS Receivers with External Sensor Augumentation

SUMMARY The filtering of the satellite range and range-rate measurements from single channel sequential global positioning system (GPS) receivers is usually done with an extended Kalman filter which has state variables defined in terms of an orthogonal navigation reference frame. An attractive suboptimal alternative is range-domain filtering, in which the individual satellite measurements are filtered separately before they are combined for the navigation solution. The main advantages of range-domain filtering are decreased processing and storage requirements, and simplified tuning. Several range filter mechanization alternatives are presented, along with an innovative approach for combining the filtered range-domain quantities to determine the navigation state estimate. In addition, a method is outlined for incorporating measurements from auxiliary sensors into the range filtering scheme which is similar to the one used for incorporating the satellite measurements themselves. A method is also described for incorporating inertial measurements into the range filtering scheme as a process driver.