High-Accuracy GPS-Based Aircraft Navigation for Landing using Pseudolites and Double-Difference Carrier Phase Measurements

The GPS code phase measurements provide accuracy about 5-20 m. This accuracy level is not sufficient for some applications such as aircraft landing. Precise positioning can be achieved by using differential carrier phase measurements. But these measurements contain unknown integers. The Carrier phase integer ambiguity can be resolved with the aid of ranging information from two integrity beacons, placed one on each side of the approach path to a runway. The clock bias present in the single difference carrier phase measurements is cancelled by the double-differencing. However, the double-difference measurements are correlated. The decorrelation is achieved by using LAMBDA method. This paper presents the integer ambiguity resolution algorithm and position estimation with single-difference and double-difference carrier phase measurements.