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    The AUSGeoid09 model of the Australian Height Datum

    147110_24964_ausgeoid2009v7-revised.pdf (904.5Kb)
    Access Status
    Open access
    Authors
    Featherstone, Will
    Kirby, Jonathan
    Hirt, Christian
    Filmer, Michael
    Claessens, Sten
    Brown, N.
    Hu, Guorong
    Johnston, G.
    Date
    2011
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Featherstone, Will and Kirby, Jonathan and Hirt, Christian and Filmer, Michael and Claessens, Sten and Brown, Nicholas and Hu, Guorong and Johnston, Gary. 2011. The AUSGeoid09 model of the Australian Height Datum. Journal of Geodesy. 85 (3): pp. 133-150.
    Source Title
    Journal of Geodesy
    DOI
    10.1007/s00190-010-0422-2
    ISSN
    09497714
    Faculty
    Department of Spatial Sciences
    Faculty of Science and Engineering
    WA School of Mines
    Remarks

    The original publication is available at : http://www.springerlink.com

    URI
    http://hdl.handle.net/20.500.11937/23487
    Collection
    • Curtin Research Publications
    Abstract

    AUSGeoid09 is the new Australia-wide gravimetric quasigeoid model that has been a posteriori fitted to the Australian Height Datum (AHD) so as to provide a product that is practically useful for the more direct determination of AHD heights from Global Navigation Satellite Systems (GNSS). This approach is necessary because the AHD is predominantly a third-order vertical datum that contains a ~1 m north-south tilt and ~0.5 m regional distortions with respect to the quasigeoid, meaning that GNSS-gravimetric-quasigeoid and AHD heights are inconsistent. Since the AHD remains the official vertical datum in Australia, it is necessary to provide GNSS users with effective means of recovering AHD heights. The gravimetric component of the quasigeoid model was computed using a hybrid of the remove-compute-restore technique with a degree-40 deterministically modified kernel over a one-degree spherical cap, which is superior to the remove-compute-restore technique alone in Australia (with or without a cap). This is because the modified kernel and cap combine to filter long-wavelength errors from the terrestrial gravity anomalies. The zero-tide EGM2008 global gravitational model to degree and order 2190 was used as the reference field.Other input data are: ~1.4 million land gravity anomalies from Geoscience Australia, 1'x1' DNSC2008GRA altimeter-derived gravity anomalies offshore, the 9"x9" GEODATA-DEM9S Australian digital elevation model, and a readjustment of Australian National Levelling Network (ANLN) constrained to the CARS2006 dynamic ocean topography model. In order to determine the numerical integration parameters for the modified kernel, the gravimetric component of AUSGeoid09 was compared with 911 GNSS-observed ellipsoidal heights at benchmarks. The standard deviation of fit to the GNSS-AHD heights is 222 mm, which dropped to 134 mm for the readjusted GNSS-ANLN heights, showing that careful consideration now needs to be given to the quality of the levelling data used to assess gravimetric quasigeoid models. The publicly released version of AUSGeoid09 also includes a geometric component that models the difference between the gravimetric quasigeoid and the zero surface of the AHD at 6,794 benchmarks. This a posteriori fitting used least-squares collocation (LSC) in cross-validation mode to determine a correlation length of 75 km for the analytical covariance function, whereas the noise was taken from the estimated standard deviation of the GNSS ellipsoidal heights. After this LSC surface-fitting, the standard deviation of fit reduced to 30 mm, one third of which is attributable to the uncertainty in the GNSS ellipsoidal heights.

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      The Australian Height Datum (AHD) was established in 1971, and is the basis for all physical heights in Australia. However, a complete revision of the AHD has never occurred, despite problems that, although not always ...
    • AUSGeoid09: a more direct and more accurate model for converting ellipsoidal heights to AHD heights
      Brown, N.; Featherstone, Will; Hu, G.; Johnston, G. (2011)
      In an absolute sense, AUSGeoid09 is an order of magnitude more accurate than AUSGeoid98 at converting ellipsoidal heights to Australian Height Datum (AHD) heights and vice versa. Results of this study show AUSGeoid09 can ...
    • GNSS-based heighting in Australia: current, emerging and future issues
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      Ellipsoidal heights, i.e., w.r.t. a geometrical Earth figure, determined from Global Navigation Satellite Systems (GNSS) are inherently their least accurate coordinate, due mainly to satellite geometry and atmospheric ...
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