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
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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|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:||28 Oct 2011 19:46|
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