Development and Testing of a Multiple Filter Approach for Precise DGPS Positioning and Carrier-Phase Ambiguity Resolution

The most precise relative positioning obtained using differential GPS depends on accurately determining carrier-phase integer ambiguities. To achieve high precision, many current static and kinematic algorithms use a floating-point solution until enough information becomes available to fix the carrier-phase ambiguities accurately. A mew method is presented that uses a multiple model Kalman filter to resolve the carrier-phase integer ambiguities. This method starts with the floating-point results, yet smoothly and rapidly attains the precision of the correct fixed-integer solution, eliminating the need to decide when to switch from the floating to the fixed-integer solution. This method is based on a theoretically correct blending of solutions from multiple filters. This new technique is computationally efficient, providing a robust navigation solution useful in demanding applications such as precision landing and autonomous navigation. The new method was evaluated during static ground and flight tests. Initial results indicate that the new method is capable of quickly resolving the carrier-phase ambiguities and provides a highly accurate (centimeter-level) navigation solution. However, the performance of the new method depends on the correct carrier-phase ambiguity set being hypothesized by one of the multiple filters. Recommendations for further research are included