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International Global Navigation Satellite Systems Association
IGNSS Conference 2016
Colombo Theatres, Kensington Campus, UNSW Australia
6 – 8 December 2016
Triple Frequency precise point positioning with
multi-constellation GNSS
Manoj Deo
PhD Candidate, Department of Spatial Sciences, Curtin University,
GPO Box U 1987, Perth WA 6845, Australia
Phone: +61 432163000
Email: manoj.deo01@gmail.com
Ahmed El-Mowafy
Assoc. Professor, Department of Spatial Sciences, Curtin University,
GPO Box U 1987, Perth WA 6845, Australia
Phone: +61 8 9266 3403
Fax: +61 8 9266 2703
Email: a.el-mowafy@curtin.edu.au
ABSTRACT
The availability of signals on three or more frequencies from multiple GNSS
constellations provides opportunities for improving precise point positioning
(PPP) convergence time and accuracy, compared to when using dual-
frequency observations from a single constellation. Although the multi-
frequency and multi-constellation (MFMC) data may be used with present day
precise orbit and clock products, there are several biases that must be
considered to get the best results. When using IGS products, the precise orbit
and clock corrections are generated using dual-frequency ionosphere-free
combinations of a ‘base’ pair of signals, and usage of other signals in the PPP
model results in differential code biases (DCB). Other biases to consider
include differential phase biases (DPB) for the satellites and receiver and
satellite antenna offsets for individual frequencies. Integrating multi-
constellation data introduces additional biases, such as inter-system hardware
and time biases and inter-frequency bias. Although the integration of MFMC
data introduces such biases, it improves the measurement model strength and
hence can potentially improve PPP performance through reducing solution
convergence time and increasing precision and accuracy.
A brief overview of the MFMC biases and strategies that may be used to treat
them is discussed. A proposed PPP model that uses triple frequency
ionosphere-free low-noise linear combination for float ambiguity estimation
is tested and analysed. MFMC data from four Australian sites is used to
demonstrate the improvements in PPP solution convergence time, accuracy
and precision, when comparing single- to multi-constellation GNSS data.
