Unification of New Zealand’s local vertical datums: iterative gravimetric quasigeoid computations |
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Authors: | M J Amos W E Featherstone |
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Institution: | (1) Land Information New Zealand, Private Box 5501, Wellington, 6145, New Zealand;(2) Western Australian Centre for Geodesy and The Institute for Geoscience Research, Curtin University of Technology, GPO Box U1987, Perth, WA, 6845, Australia |
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Abstract: | New Zealand uses 13 separate local vertical datums (LVDs) based on geodetic levelling from 12 different tide-gauges. We describe
their unification using a regional gravimetric quasigeoid model and GPS-levelling data on each LVD. A novel application of
iterative quasigeoid computation is used, where the LVD offsets computed from earlier models are used to apply additional
gravity reductions from each LVD to that model. The solution converges after only three iterations yielding LVD offsets ranging
from 0.24 to 0.58 m with an average standard deviation of ±0.08 m. The so-computed LVD offsets agree, within expected data
errors, with geodetically levelled height differences at common benchmarks between adjacent LVDs. This shows that iterated
quasigeoid models have a role in vertical datum unification. |
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Keywords: | Vertical datum unification Iterative quasigeoid computation Geodetic levelling |
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