International Global Navigation Satellite Systems Association
IGNSS Conference 2016
Colombo Theatres, Kensington Campus, UNSW Australia
6 – 8 December 2016
Ambiguity Resolution (PPP-AR) For Precise Point
Positioning Based on Combined
GPS Observations
Shuyang Cheng and Jinling Wang
School of Civil and Environmental Engineering, University of New South Wales,
Sydney, NSW 2052, Australia
Phone: +61 416 866 545 Fax: +61 2 9385 6139 Email: shuyang.cheng@student.unsw.edu.au
ABSTRACT
Precise point positioning (PPP) which uses ionosphere-free combination has
been investigated for many years. In such conventional PPP model, the
ambiguity parameters cannot be resolved to integers due to uncalibrated
phase biases. These biases can be compensated by decoupled satellite clock
(DSC), or fractional cycle bias (FCB), or integer recovery clock (IRC).
These bias compensations are all based on ionosphere-free PPP (IF-PPP) and
Melbourne-Wubbena combination in which the wide-lane (WL) ambiguity
and narrow-lane (NL) ambiguity are fixed successively. Their performances
with numerical analysis need to be further investigated. In addition, the
vertical accuracy with PPP-AR is much worse than the horizontal
component due to many factors, one of which is the limited accuracy of
troposphere correction or weak zenith wet delay (ZWD) estimation.
In this study, the IRC and FCB based PPP-AR methods with ionosphere-free
PPP are systematically compared. Firstly, we introduce the integer property
recovery of these methods to justify their equivalence. Moreover,
numerical analysis is conducted to evaluate the performances of these
methods. The results indicate that although these methods are equivalent in
theory, the performance is slightly different due to the biased property of
FCB estimation and different processing strategies in IRC based PPP-AR.
Furthermore, it is demonstrated that vertical positioning accuracy can be
improved with proper troposphere constraints.
KEYWORDS: Precise Point Positioning, Integer Ambiguity Resolution,
Fractional Cycle Bias, Integer Recovery Clock, Troposphere Delay
Constraint
