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Stanaway R.,University of New South Wales | Roberts C.,University of New South Wales | Blick G.,Land Information New Zealand
International Association of Geodesy Symposia | Year: 2014

This paper describes a schema for a gridded absolute deformation model (ADM) and non-linear deformation patch model that can be used to transform point positions captured in the International Terrestrial Reference Frame (ITRF), or other closely aligned reference frame, to a reference epoch consistently over time for practical applications. The schema described utilises existing models of rigid plate motion, plate boundary deformation and non-linear deformation (e.g. coseismic and postseismic effects or subsidence). Application of an ADM and patchmodel can enable consistent Precise Point Positioning (PPP) over time and seamless integration of Continuously Operating Reference Station (CORS) networks within deforming zones. The strategy described can also ensure consistency of time-tagged spatial datasets (e.g. laser scanned point clouds and digital cadastral databases) and GIS within a kinematic environment. An ADM can also be used as the basis for static epoch projections of a national or regional kinematic datum. A case study from New Zealand is described. © Springer-Verlag Berlin Heidelberg 2014. Source


Petrov L.,NASA | Phillips C.,CSIRO | Tzioumis T.,CSIRO | Stansby B.,Curtin University Australia | And 10 more authors.
Publications of the Astronomical Society of Australia | Year: 2011

We report the results of a successful 7-hour 1.4GHz Very Long Baseline Interferometry (VLBI) experiment using two new stations, ASKAP-29 located in Western Australia and WARK12M located on the North Island of New Zealand. This was the first geodetic VLBI observing session with the participation of these new stations. We have determined the positions of ASKAP-29 and WARK12M. Random errors on position estimates are 150-200 mm for the vertical component and 40-50 mm for the horizontal component. Systematic errors caused by the unmodeled ionosphere path delay may reach 1.3m for the vertical component. © 2011 Astronomical Society of Australia. Source


Tenzer R.,University of Otago | Vatrt V.,Military Geographic and Hydrometeorogic Office | Amos M.,Land Information New Zealand
International Association of Geodesy Symposia | Year: 2012

We utilize the geopotential value approach to determine the average offsets of 12 major local vertical datums (LVDs) in New Zealand (NZ) relative to the world height system (WHS). The LVD offsets are estimated using the EGM2008 global geopotential model coefficients complete to degree 2159 of spherical harmonics and the GPS-levelling data. WHS is defined by the adopted geoidal geopotential value W0 = 62636856 m2s-2. Our test results reveal that the average offsets of 12 major LVDs situated at the South and North Islands of NZ range from 0.01 m (Wellington 1953 LVD) to 0.37 m (One Tree Point 1964 LVD). The geopotential value of the tide-gauge station used as the origin for the LVD Wellington 1953 is thus almost the same as the geoidal geopotential value W0. EGM2008 and GPS-levelling data are further used to compute the differences between the NZGeoid05 regional quasigeoid model and the EGM2008 global quasigeoid model. The same analysis is done for NZGeoid2009 which is the official national quasigeoid model for NZ. The systematic bias of about 0.56 m is found between NZGeoid05 and EGM2008. A similar systematic bias of about 0.51 m is confirmed between NZGeoid2009 and EGM2008. © Springer-Verlag Berlin Heidelberg 2012. Source


Claessens S.J.,Curtin University Australia | Hirt C.,Curtin University Australia | Amos M.J.,Land Information New Zealand | Featherstone W.E.,Curtin University Australia | Kirby J.F.,Curtin University Australia
Survey Review | Year: 2011

The NZGeoid09 gravimetric quasigeoid model of New Zealand was computed through FFT-based Stokesian integration with a deterministically modified kernel and an iterative computation approach that accounts for offsets among New Zealand's 13 different local vertical datums (LVDs). NZGeoid09 is an improvement over the previous NZGeoid05 due to use of the EGM2008 and DNSC08GRA models, and due to improvements to the data processing strategy. The integration parameters of degree of kernel modification L = 40 and cap radius ψ0=2. 5° were determined empirically through a comparison with 1422 GPS/levelling observations, after the LVD offsets had been removed. The precision of NZGeoid09 was assessed using the same GPS/levelling dataset, yielding an overall standard deviation of 6.2 cm. NZGeoid09 performs better than NZGeoid05 and marginally better than EGM2008, but few data are available in the Southern Alps of New Zealand to give a better evaluation. © 2011 Maney Publishing. Source


Denys P.,University of Otago | Denham M.,University of Otago | Amos M.,Land Information New Zealand
Journal of Spatial Science | Year: 2010

To facilitate day to day surveying and mapping activities, Land Information New Zealand (LINZ) has developed a regional quasigeoid (NZGeoid05) by enhancing a global geopotential model with satellite, terrestrial and sea gravity data over the continental shelf of New Zealand (NZ). The overall national precision of NZGeoid05 was estimated by LINZ to be ±0.08 m (1σ). Six regions, distributed throughout the South Island of NZ, have been used to provide further independent verification of the precision of the NZGeoid05 by determining the geometric geoid-ellipsoid separation. In each region, several benchmarks with first-order normal-orthometric heights were selected and ellipsoidal heights measured independently using geodetic position techniques. A comparison has also been made with the global geopotential model, EGM2008. For NZGeoid05, four of the six regions tested have a RMS fit better than ±0.05 m, while for the EGM2008 this is only achieved in two regions. The estimated geoid slopes for both the NZGeoid05 and EGM2008 models agree with the geometric data to better than 1 cm/km in five of the six regions tested. © 2010 Surveying and Spatial Sciences Institute and Mapping Sciences Institute, Australia. Source

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