Kalman-Filter-Based Integer Ambiguity Resolution Strategy for Long-Baseline RTK with Ionosphere and Troposphere Estimation

The performance of RTK with long baseline over 100 km is much degraded compared to conventional short-range RTK. The authors have developed a new strategy for such long baseline RTK applicable to up to 1,000 km baselines. The strategy consists of an EKF-based parameter estimator without generating any linear combination of the measurements. The strategy also includes the integer ambiguity resolution in carrier-phase measurements with the partial fixing feature and tight constraints to once fixed integer ambiguities. To verify and demonstrate the proposed strategy, we conducted some online tests and online real-time tests for the various baseline lengths in the range of from 29.9 km to 1,099.9 km. The results of these tests indicates that the proposed strategy works well up to 1,000 km baseline. The performance of such the long baseline RTK, however, is degraded especially in summer time. Further improvement is necessary to establish the strategy as a reliable and robust technique.