An evaluation of orthometric height accuracy using bore hole gravimetry

Strange, William E.

doi:10.1007/bf02525730

Cited by 13 publications

(10 citation statements)

References 3 publications

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“…However, a true orthometric height cannot be computed exactly (e.g., Jekeli 2000), becauseḡ is inside the topography and cannot be measured (cf. Strange 1982;Tenzer et al 2005). There are a number of different methods of approximatingḡ, resulting in several variants of orthometric heights (e.g., Helmert 1890;Neithammer 1932;Mader 1954; Strang van Hees 1992; Kao et al 2000;Hwang and Hsiao 2003;Tenzer et al 2005).…”

mentioning

confidence: 99%

The effect of EGM2008-based normal, normal-orthometric and Helmert orthometric height systems on the Australian levelling network

Filmer

Featherstone

Kühn

2010

J Geod

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This paper investigates the normal-orthometric correction used in the definition of the Australian Height Datum (AHD), and also computes and evaluates normal and Helmert orthometric corrections for the Australian National Levelling Network (ANLN). Testing these corrections in Australia is important to establish which height system is most appropriate for any new Australian vertical datum. An approximate approach to assigning gravity values to ANLN benchmarks (BMs) is used, where the EGM2008-modelled gravity field is used to 're-construct' observed gravity at the BMs. Network loop closures (for first-and second-order levelling) indicate reduced misclosures for all height corrections considered here, particularly in the mountainous regions of south eastern Australia. Differences between Helmert orthometric and normal-orthometric heights reach 44 cm in the Australian Alps, and differences between Helmert orthometric and normal heights are about 26 cm in the same region. Normal-orthometric heights differ from normal heights by up to 18 cm in mountainous regions > 2000 m. This indicates that the quasigeoid is not compatible with normalorthometric heights.

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confidence: 99%

The effect of EGM2008-based normal, normal-orthometric and Helmert orthometric height systems on the Australian levelling network

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Featherstone

Kühn

2010

J Geod

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“…This requires knowledge of gravity variations (cf. Strange, 1982) or mass-density distribution (cf. Sünkel, 1986;Allister and Featherstone, 2001) inside the topography.…”

Section: Height Systems Related To Gravity: Natural or Physical Heightsmentioning

confidence: 99%

Height systems and vertical datums: A review in the Australian context

Featherstone¹,

Kühn

2006

Journal of Spatial Science

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This paper reviews (without equations) the various definitions of height systems and vertical geodetic datum surfaces, together with their practical realisation for users in Australia. Excluding geopotential numbers, a height system is a one-dimensional coordinate system used to express the metric distance (height) of a point from some reference surface. Its definition varies according to the reference surface chosen and the path along which the height is measured. A vertical geodetic datum is the practical realisation of a height system and its reference surface for users, nominally tied to mean sea level. In Australia, the normal-orthometric height system is used, which is embedded in the Australian Height Datum (AHD). The AHD was realised by the adjustment of ~195,000 km of spirit-levelling observations fixed to limited-term observations of mean sea level at multiple tide-gauges. The paper ends by giving some explanation of the problems with the AHD and of the differences between the AHD and the national geoid model, pointing out that it is preferable to recompute the AHD.

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“…where g is the mean gravity along the plumb line (inside the Earth). As g cannot be observed directly (besides some stations with borehole gravity data; Strange 1982), hypotheses about the interior gravity field are necessary, which is one of the main drawbacks of the orthometric heights. Assuming a constant density of the topographic masses (2670 kg m -3 ) as well as a flat topography (so-called Poincaré-Prey reduction) leads to…”

Section: The Geoid and Heightsmentioning

confidence: 99%

Regional Gravity Field Modeling: Theory and Practical Results

Denker

2012

Sciences of Geodesy - II

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An evaluation of orthometric height accuracy using bore hole gravimetry

Cited by 13 publications

References 3 publications

The effect of EGM2008-based normal, normal-orthometric and Helmert orthometric height systems on the Australian levelling network

The effect of EGM2008-based normal, normal-orthometric and Helmert orthometric height systems on the Australian levelling network

Height systems and vertical datums: A review in the Australian context

Regional Gravity Field Modeling: Theory and Practical Results

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