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CURRENT RESEARCH PROJECTS AND RECENT RESULTSThe research programs and projects listed on this web-page include some of our latest results and preprints of papers submitted to journals. The core research areas of The Western Australian Centre for Geodesy comprise gravity field determination, precise satellite positioning, and deformation monitoring. However, we have demonstrated research expertise in many other areas.If you are a prospective employee or student who is interested in joining Western Australian Centre for Geodesy, please read our opportunites page for potential projects and funding details, or contact Professor Will Featherstone to discuss opportunities.
Gravity Field and Height Determination
GRAVITY FIELD AND HEIGHT DETERMINATION Following our work on AUSGeoid98 (free download and technical description), we continue to refine our theories, computational techniques and software to compute regional gravimetric geoid models. Our recent studies have concentrated on the improvements offered by new data sources, such as the version 2 DEM of Australia, dedicated satellite gravity data, identification and removal of erroneous marine gravity data. In collaboration with Land Information New Zealand, we are also working on the first regonal gravimetric geoid for New Zealand for over a decade.
Relevant papers:
Project home-page: not yet available Potential PhD project (PDF)
Synthetic [Simulated] Gravity Field Modelling The aim of this project is to construct a synthetic, error-free gravity field model of the Earth's gravity field, which can be used to calibrate and validate the various gravity-field determination theories and techniques used around the world. This is as part of the International Association of Geodesy's Special Study Group 3.177. The Western Australian Centre for Geodesy has concentrated predominantly on the production of synthetic 'effects' models that are based on high-degree spherical harmonic expansions. These have have been used to validate geoid determination techniques in Australia and Canada.
Relevant papers:
Project home-page
Potential PhD project (PDF)
Lithospheric Elastic Thickness via the Wavelet Transform Existing methods of determining the Earth's isostatic response to loading assume ideal but unrealistic conditions. This project seeks to improve upon these methods by considering the anisotropy of the lithosphere, its loads, and the method of analysis. Instead of using the conventional one-dimensional Fourier transform method of correlating gravity and topography data, a two-dimensional wavelet transform method has been perfected, with the ability to generate maps of plate strength. Fractal and multifractal synthetic models representing the Earth will be used to test the method, prior to an investigation of lithospheric anisotropy in Australia and the western United States. The results are expected to improve our understanding of tectonic processes in these areas, with positive benefits to Australia's resource industries.
Relevant papers:
Swain, C.J. and J.F. Kirby (2003). The coherence method using a thin anisotropic elastic plate model, Geophysical Research Letters, 30(19), 2014, doi: 10.1029/2003GL018350.
Improved Height Definition and Determination This project interfaces with the above project on refined geoid modelling. However, it aims to improve the determination of heights from GPS techniques by adapting the gravimetric geoid model to fit the local vertical datum. In Australia, for example, there are disceptancies of over one-metre among AUSGeoid98, GPS and the Australian Height Datum. The combined approach will yield a surface that is better suited to the direct transformation of heights without the need for post-survey corrections or adjustments. Recent studies have identified several suitable geostatitical surfaces to model the discrepancies between the gravimetric geoid and the local vertical datum. We are also interested in then proper definition and realisation of height systems such that they are fully compatible with gravimetric geoid models.
Relevant papers:
Project home-page: not yet available
Potential PhD project 1 (PDF)
Gravimetric Terrain Corrections In 1999, we computed the first ever Australia-wide grid of gravimetric terrain corrections. However, their spatial resoltion had to be reduced to 750m due to errors in the then-available DEM. With the release of the version 2 Australian DEM, we have computed a new high-resolution (250m) nation-wide grid of gravimetric terrain corrections. These have been supplied to Geoscience Australia for inclusion in the national gravity database, and will also be used for refined Australian geoid models. Future work plans to trial more sophisticated algorithms, as well as considering the far-field effects over the entire Earth.
Relevant papers:
Project home-page: not yet available Potential PhD project (PDF)
Modified Integration Kernels Our work on the role of modified kernels in gravimetric geoid determination continues. A renewed impetus for this has come from the current and planned dedicated satellite gravity field misions (GRACE, CHAMP, GOCE), where the modified kernels can be used as optimised filters to reduce the contamination by errors from terrestrial gravity data. We are also trialing band-limited stochastically modified kernels that take into account the different data errors in those parts of the gravity field spectrum where they are known. These studies include the theoretical formulation of modified kernels, supported by empirical studies of their performance in practical gravimetric geoid computation.
Relevant papers:
Project home-page: not yet available
Potential PhD project (PDF)
Gravimetric Satellite Altimetry Recent experiments to determine the best grid of satellite altimter-derived gravity anomalies to use in future Australian geoid models have uncovered some quite significant differences among the gravity anomalies produced by different groups around the world. These differences reach over 100 mGal in the coastal regions of Australia. These are to be expected given the problems with radar tracking in the caostal zone (among other factors). Our results show that the altimeter waveform returns are contaminated (by the coastal sea surace state and radar backscatter from the land) out to a distance of 20 km offshore Australia. Work is ongong to solve this problem through retracking the coastal waveforms.
Relevant papers:
Gravity Anomaly Definition We have revisited the definition and use of gravity anomalies and gravity disturbances in both geodesy and geophysics. This has shown that there are some differences between the definitions and uses of these quantities between these disciplines, which can now be taken into account. Our reserach in this area also includes the computation of gravimetric terrain corrections(described above) and the investigated the optimal ways to coordinate gravity observations using GPS techniques.
Relevant papers:
PRECISE POSITIONING FROM SATELLITES The National GPS Receiver Facility As part of a collaborative venture among The University of New South Wales, Curtin University of Technology, The University of Tasmania, The University of Canberra and The Australian National University, we have access to 10 Leica CRS1000 dual-frequency GPS receivers. These instruments are being used for a number of joint projects, including monitoring of deformation of man-made structures and natural features, global and regional plate tectonics, measurement of sea-level change, precise mapping of Antarctic ice sheets and their flow, and sounding of the Earth's atmosphere.
Relevant paper:
GNSS Calibration, Validation and Quality Control A facility for testing and validating GNSS (Global Navigation Satellite Systems) hardware, software/firmware and operators has been established on and close to the Bentley Campus of Curtin University of Technology. This comprises a network of fixed pillars that can be used for testing static-based GNSS positioning and a network of ground marks that can be used for testing real-time stop-and-go kinematic (RTK) GNSS positioning. We have demonstrated that RTK GPS systems remain subject to errors that are not reported to the operator, such as incorrect integer ambiguity resolution. Therefore, users must remain sceptical about the positional accuracy reported by such systems.
Relevant papers:
Project home-page: not yet available
GPS Meteorology Although the tropospheric delay is a nuisance parameter in precise satellite positioning, it is a useful signal for climatic and meteorological applications. We are currently using data from permanent Australian GPS networks, including that maintained and operated by Geoscience Australia (formerly AUSLIG), to estimate the amount of atmospheric water vapour in a near real-time mode. These data are being supplied to the Bureau of Meteorology Research Centre to provide extra information for their atmospheric models, with the view to improved weather forecasting for Australia.
Relevant papers:
Project home-page: not yet available Stochastic Modelling of GNSS Data
Stochastic modelling is critical to ensure the accuracy, precision and reliability of both real-time and
post-processed GNSS position solutions. Our recent theoretical work indicates that the correct estimation
of stochastic models, namely the correlation between observations, significantly improves the reliability
of existing GNSS data processing techniques. Errors in the GNSS functional models, such as antenna
phase-centre variations, multipath of satellite signals and satellite orbital errors, all combine to degrade
the precision of satellite positioning solutions. We are addressing the mitigation of such errors using
techniques that include advanced digital signal processing and filtering, penalised least squares, improved
stochastic modelling, and neural networks.
Relevant papers:
Project home-page 1:
static applications GNSS Integer Ambiguity Resolution
Correct estimation of the set of integer phase ambiguities is critical for all centimetre-level
GNSS positioning. For example, the effect of incorrect ambiguity resolution by RTK GPS systems
was shown on our GNSS testing facility (above). Our recent research work has focussed on more
sophisticated and robust techniques for the identification of the correct set of integer
ambiguities for both static an kinematic applciations of GNSS positioning.
Relevant papers:
Project home-page 1:
Ambuguity validation
DEMs from Satellite Altimetry This project is in collaboration with the Geomatics Unit at De Montfort University (England) and funded by an Australian Resrearch Council IREX grant. This grant allows for the (funded) exchange of staff and students between the two institutions. Our initial results have been for the validation of several digital elevation models (DEMs) over Australia using ERS-1 satellite altimetry over land. This has revealed some quite serious deficiencies in most of the global DEMs that cover Australia. Our recent work has focussed on providing empirical correction coefficients to the EGM96 global geopotential model to account for a disparity in the JGP95E DEM along the 140E meridian over Australia.
Relevant paper:
DEFORMATION MONITORING USING GEODETIC AND PHOTOGRAMMETRIC TECHNIQUES This new technology offers a rapid means of measuring deformations of entire surfaces, such as dam walls, open-pit mine walls and built structures. Laser scanners provide several million three-dimensional point measurements of a laser-reflective surface in a matter of minutes using pulsed laser ranging techniques. We are currently developing intelligent filtering algorithms to automatically extract surface deformations from the laser scanner point clouds. Importantly, the surface deformations estimated by the laser scanner are also being controlled and calibrated by discrete-point measurements from terrestrial and satellite-based positioning systems. Initial results indicate that this integrated technique can identify and measure surface deformations that were previously undetected using existing techniques.
Relevant papers:
Geodynamics of the South-west Seismic Zone, Western Australia The south-west seismic zone (SWSZ) in Western Australia is one of the intra-plate tectonic regions in the world where earthquake activity occurs that is not associated with the plate boundaries. Importantly, the proximity of the SWSZ zone to Perth presents a significant seismic hazard. At present, the magnitude and type of deformation of the Earth’s crust that is occurring in this region are not fully understood. In collaboration with the University of Western Australia, Geoscience Australia, the Western Australian Department of Land Administration, and the New Zealand Institute for Geological and Nuclear Sciences have initiated a long-term monitoring project using repeat GPS and gravity measurements throughout the SWSZ. The first GPS campaign was conducted in May 2002, and occupied 50 permanent monuments distributed across the SWSZ.
Relevant papers:
Project home-page (with UWA)
Potential PhD project (with UWA)
Satellite Radar Interferometry Synthetic aperture radar interferometry (InSAR) is a technique that enables generation of Digital Elevation Models (DEM) and detection of surface motion at the centimetre level using radar signals transmitted from a satellite or an aeroplane. Deformation observations can be performed due to the fact that surface motion, caused by natural and human activities, generates a local phase shift in the resultant interferogram. The magnitude of surface deformation can be estimated directly as a fraction of the wavelength of the transmitted signal. Moreover, differential InSAR (DInSAR) eliminates the phase signal caused by relief to yield a differential interferogram in which the signature of surface deformation can be seen. Although InSAR applications are well established, the improvement of the interferometry technique and the quality of its products is highly desirable to further enhance its capabilities. The application of InSAR encounters problems due to noise in the interferometric phase measurement, caused by a number of decorrelation factors. In addition, the interferogram contains biases owing to satellite orbit errors and atmospheric heterogeneity. These factors dramatically reduce the effectiveness of radar interferometry in many applications, and, in particular, compromise detection and analysis of small-scale spatial deformations. The research aims to apply radar interferometry processing to detect small-scale surface deformations, improve the quality of the interferometry products, determine the minimum and maximum detectable deformation gradient and enhance the analysis of the interferometric phase image.
Relevant papers:
Open-pit Mine-wall Deformation Monitoring Steep-slope stability monitoring is of importance to Australia, in terms of safety to the general public and in the mining industry. Over recent years, we have designed, developed and tested a low-cost, continuous GPS deformation monitoring system for use on potentially unstable steep slopes, such as open-pit mine walls, dam walls, built structures and earth/rock slopes. A prototype of this system was currently installed in the WMC open-pit nickel mine at Mount Keith, Western Australia. This system successfully detected deformation of an entire wall, which was confirmed by terrestrial geodetic measurements.
Relevant papers:
Project home-page 1:
project description
OTHER GEODETIC RESEARCH PROJECTS AND PREPRINTS Back to The Western Australian Centre for Geodesy home-page |
