Generation of network-based differential corrections for regional GNSS services

Zheng, Yi (2007) Generation of network-based differential corrections for regional GNSS services. PhD thesis, Queensland University of Technology.


Network-based Differential GPS (DGPS), regardless of its global, regional or local

scales, is enabling technology to improve GPS positioning accuracy from tens of

meters, to the levels of meters, decimetres and centimetres level in real time,

depending on geographical coverage of the network and measurement types. The

method is to use the data from a permanent network of reference stations to

model errors due to inaccurate GPS satellite orbit ephemeris and clock data,

ionospheric and tropospheric effects as well as other GPS satellite and receiver

biases. Then error correction messages can be sent to users via any communication

link in real time.

This PhD research involves algorithm development for generating satellite orbit

and tropospheric delay corrections using a regional or local reference network,

especially tropospheric grid corrections, which have not been included in the

existing DGPS correction vector messages, for the next generation of regional

GNSS positioning services. Contributions of the research are made in the following

three areas:

First of all, research has been undertaken to test orbit interpolation methods, in

order to represent GPS orbits and orbital corrections accurately and efficiently for

(near) real-time GPS applications. For precise and predicted GPS orbits given in

SP3 format and orbital corrections with respect to the broadcast ephemeris,

numerical tests were conducted using different terms of Lagrange, Chebyshev and

trigonometric polynomial functions.

Secondly, this research has implemented a short-arc (9-hour) sliding-window

orbit monitoring strategy to identify larger orbit errors in the predicted part of

IGS ultra-rapid orbit solutions in near real time, using GPS tracking data from a

regional network around Australia. The strategy is to predict the uncertainty

estimates of each orbit over a short orbit arc in near real time, which allows

users to down-weight the problematic satellites and reduces the effects of orbital errors for improved near real time ZTD estimation. Unlike long-arc orbit determination,

we only estimate 6 orbital elements for each satellite.

Finally, this research has proposed a new tropospheric delay correction model,

which uses the Ordinary Kriging (OK) method to interpolate the residual ZTD

within a regional area GPS network to improve the positioning accuracy. ZTD

estimates from 129 EUREF Permanent Network (EPN) stations across Europe for

over 3 months and from 17 GPSnet reference stations (Victoria, Australia) for

one week were collected and processed for this study, respectively. It is concluded

that interpolating residual ZTD is an efficient way to improve regional area

differential GPS positioning.

Impact and interest:

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ID Code: 16359
Item Type: QUT Thesis (PhD)
Supervisor: Feng, Yanming & Moody, Miles
Keywords: network-based, regional GNSS, GPS, DGPS
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Department: Faculty of Built Environment and Engineering
Institution: Queensland University of Technology
Copyright Owner: Copyright Yi Zheng
Deposited On: 03 Dec 2008 04:01
Last Modified: 24 Jun 2017 14:39

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