Precise Point Positioning; Ambiguity Resolution; Rapid Re-Convergence; Predicted Ionospheric Delays; Global Positioning System
Abstract :
[en] Integer ambiguity resolution at a single station can be preformed if the fractional-cycle biases are separated from the ambiguity estimates in precise point positioning (PPP). Despite the improved positioning accuracy by such integer resolutions, the convergence to an ambiguity-fixed solution normally requires at least a few tens of minutes. More importantly, such convergences can repeatedly occur on the occasion of losses of tracking locks for many satellites if an open sky-view is not constantly available, consequently totally destroying the practicability of real-time PPP. In this study, in case of such re-convergences, we develop a method in which ionospheric delays are precisely predicted to significantly accelerate integer ambiguity resolutions. The effectiveness of this method consists in two aspects: First, wide-lane ambiguities can be rapidly resolved using the ionosphere- corrected wide-lane measurements, instead of the noisy Melbourne-Wübbena combination measurements; second, narrow-lane ambiguity resolution can be accelerated under the tight constraints derived from the ionosphere-corrected unambiguous wide-lane measurements. In the tests at 90 static stations suffering from simulated total loss of tracking locks, 93.3% and 95.0% of re- convergences to wide-lane and narrow-lane ambiguity resolutions can be achieved within 5 s, respectively, even though the time latency for the predicted ionospheric delays is up to 180 s. In the tests at a mobile van moving in a GPS-adverse environment where satellite number significantly decreases and cycle slips frequently occur, only when the predicted ionospheric delays are applied can the rate of ambiguity-fixed epochs be dramatically improved from 7.7% to 93.6% of all epochs. Therefore, this method can potentially relieve the unrealistic requirement of a continuous open sky- view by most PPP applications and improve the practicability of real-time PPP.
Disciplines :
Earth sciences & physical geography
Identifiers :
UNILU:UL-ARTICLE-2011-058
Author, co-author :
Geng, J.; University of Nottingham > Institute of Engineering Surveying and Space Geodesy
Meng, X.; University of Nottingham > Institute of Engineering Surveying and Space Geodesy
Dodson, A. H.; University of Nottingham > Institute of Engineering Surveying and Space Geodesy
Ge, M.
Teferle, Felix Norman ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Engineering Research Unit
Language :
English
Title :
Rapid re-convergences to ambiguity-fixed solutions in precise point-positioning