Integer satellite clock combination for Precise Point Positioning with ambiguity resolution

While satellite clock combinations are routinely utilized within the IGS, they currently disregard the fact that some ACs provide integer clocks. Users have been expected to choose either a robust combined solution or select individual AC solutions that provide integer clocks allowing the user to compute a PPP-AR solution. The goal of our investigation was to develop and test a robust satellite clock combination preserving the integer nature of the clocks and therefore the carrier-phase ambiguities at the user end. Two sets of combined clock products were generated: 1) combined integer satellite clock products, and 2) IGS clocks aligned to integer clocks. The combined products were evaluated in the position domain by processing GPS data from 29 IGS stations, observed during DOY 178 to 184 of 2016. mm-level differences were noted, which was expected as the strength lies mainly in its reliability and stable median performance and the combined product is better than or equivalent to any single AC's product in the combination process. IGS clock products aligned to an AC integer clocks yielded the best PPP-AR results, for both static and kinematic solutions.