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International Global Navigation Satellite Systems Association
IGNSS Symposium 2018
Colombo Theatres, Kensington Campus, UNSW Australia
7 – 9 February 2018
Performance Evaluation of AUSGeoid2020 in NSW
Volker Janssen
Spatial Services
NSW Department of Finance, Services & Innovation, Bathurst NSW 2795, Australia
Tel: +61-2-6332 8426, Email: Volker.Janssen@finance.nsw.gov.au
Tony Watson
Spatial Services
NSW Department of Finance, Services & Innovation, Bathurst NSW 2795, Australia
Tel: +61-2-6332 8232, Email: Tony.Watson@finance.nsw.gov.au
ABSTRACT
Presently, Australia is transitioning to a modernised national datum in order
to meet the increasing demands placed by modern satellite-based positioning
technology on the underlying geodetic framework. The much improved
Geocentric Datum of Australia 2020 (GDA2020) was released in December
2017 and is to replace the current national datum (GDA94) in practice by
2020. This also includes a new quasigeoid model, AUSGeoid2020, to
provide an improved connection between ellipsoidal heights derived from
Global Navigation Satellite System (GNSS) observations and the Australian
Height Datum (AHD). In September 2017, Geoscience Australia finalised
the release version of AUSGeoid2020. This paper quantifies the expected
improvement of using AUSGeoid2020 in conjunction with GDA2020
ellipsoidal heights over using the current AUSGeoid09 in conjunction with
GDA94 ellipsoidal heights to access AHD in New South Wales (NSW).
Three tests are performed in order to investigate how well the two
quasigeoid models fit known AHD heights across NSW in practice, based on
(1) 138 CORSnet-NSW sites, (2) seven GNSS-based network adjustments of
varying extent and size, and (3) numerous height control points from these
adjustments. It is shown that the AUSGeoid2020 product provides a
considerably improved fit to AHD across NSW when compared to its
predecessor. However, the rigorous uncertainty values provided with
AUSGeoid2020 appear to be overly pessimistic, resulting in the
AUSGeoid2020 uncertainty grid having only limited practical value at this
stage.
KEYWORDS: GDA2020, AUSGeoid2020, Australian Height Datum, GNSS,
CORS, datum modernisation.
