Improvement of the geoid model over Japan using integral formulae and combination of GGMs

Odera, Patroba Achola

doi:10.1186/1880-5981-66-22

Cited by 6 publications

(9 citation statements)

References 14 publications

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“…differences between gravimetric and GPS/levelling geoid undulations using Helmert orthometric heights (Odera and Fukuda 2014) are also given in Table 2. Table 2 shows that there is a slight improvement in the standard deviation in all the regions (Hokkaido, North Honshu, Central Honshu, West Honshu, Shikoku and Kyushu), with Central Honshu (a mountainous region) having the largest improvement (from ±7.1 to ±6.9 cm), when rigorous orthometric heights are used.…”

Section: Resultsmentioning

confidence: 99%

“…The rigorous orthometric heights at the 816 GPS/levelling points are then used in the comparisons between gravimetric and GPS/levelling geoid undulations (Table 2) using the recent geoid model over Japan (Odera and Fukuda 2014). For comparison purposes, the statistics of the Figure 5 Spatial distribution of corrections to Helmert orthometric heights using 816 precise levelling points over Japan (units in cm).…”

Section: Resultsmentioning

confidence: 99%

“…This paper describes the procedure for determining corrections to Helmert orthometric heights at 816 GPS/levelling points over Japan. Comparisons between GPS/levelling and gravimetric geoid undulations (Odera and Fukuda 2014) are also presented. In this case, both Helmert and rigorous orthometric heights have been used for the comparisons.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Helmert and rigorous orthometric heights over Japan

Odera

2015

Earth, Planets and Space

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The local vertical datum in Japan is based on the Helmert's approximation of mean gravity along the plumbline. However, determination of a rigorous orthometric height requires that the integral-mean value of gravity along the plumbline between the geoid and the Earth surface has to be known precisely. An attempt has been made to obtain rigorous orthometric heights at 816 GPS/levelling points distributed over four main islands of Japan (Hokkaido, Honshu, Shikoku and Kyushu) by applying corrections to the Helmert orthometric heights. The corrections to Helmert orthometric heights are evaluated from the differences between the integral-mean gravity and the approximate mean gravity along the plumbline. The corrections to Helmert orthometric heights vary from −30.9 cm to 0.0 cm with a mean value of −0.4 cm and standard deviation of ±1.7 cm. An improved high-resolution gravimetric geoid model covering four main islands of Japan from our previous study is used to compare the consistency of the two height systems to a regionally defined gravimetric geoid model. The standard deviation of the differences between gravimetric and GPS/levelling geoid undulations is ±7.5 cm, when Helmert orthometric heights are used. The standard deviation of the differences between gravimetric and GPS/levelling geoid undulations reduces to ±7.3 cm, when rigorous orthometric heights are used. This indicates that rigorous orthometric heights are more consistent with the gravimetric geoid model than Helmert orthometric heights.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Comparison of Helmert and rigorous orthometric heights over Japan

Odera

2015

Earth, Planets and Space

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“…Development and applications of LSC techniques in geodesy and related fields have been studied by several authors (e.g. Krarup 1969;Moritz 1973;Tscherning 1976;Kearsley 1977;Moritz 1980;Knudsen 1987;Forsberg 1987;Schaffrin 1989).…”

Section: Planar Fitting and Offsets Methodsmentioning

confidence: 99%

Recovery of orthometric heights from ellipsoidal heights using offsets method over Japan

Odera

2015

Earth Planet Sp

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One of the most important applications of a geoid model is a recovery of orthometric heights from ellipsoidal heights (normally obtained from GNSS). The application of the geoid model for recovering orthometric heights from ellipsoidal heights is normally achieved by fitting the geoid model to a local vertical datum. The fitting procedure is usually accomplished by least squares collocation (LSC), using planar or spherical covariance functions. This procedure warps the gravimetric geoid model onto the local vertical datum, hence the local geoid model derived by this procedure, though convenient for local applications, it is not an equipotential surface. We propose offsets method for practical orthometric height recovery from a geoid model. The proposed procedure is more realistic because it does not constrain the local geoid to be coincident to the local vertical datum. We compare the performance of plannar fitting and offsets methods over Japan using a cross-validation procedure. Results show that offsets method performs better than the normally used planar fitting in the recovery of orthometric heights from ellipsoidal heights using a geoid model. The standard deviations of the differences between established and converted orthometric heights at randomly selected GPS/levelling test points over Japan are ±4 and ±3 cm for planar fitting and offsets methods, respectively. The offsets method is therefore more appropriate for converting ellipsoidal heights to orthometric heights than the planar fitting in the area of study.

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“…Following the successful operation of a dedicated satellite gravity mission, called-Gravity field and steady-state Ocean Circulation Explore (GOCE)-during 2009-2013, a number of GGMs with high accuracy and high spatial resolution have been released by research institutes and universities. Odera and Fukuda (2014) first employed a GOCE-based GGM for the determination of the geoid undulation over the Japanese archipelago and demonstrated that utilization of the latest GOCE-based GGM could improve the accuracy of the gravimetric geoid model for Japan.…”

Section: Introductionmentioning

confidence: 99%

Refinement of a gravimetric geoid model for Japan using GOCE and an updated regional gravity field model

Matsuo

Kuroishi

2020

Earth Planets Space

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We developed a refined gravimetric geoid model for Japan on a 1 × 1.5 arc-minute (2 km) grid from a GOCE-based satellite-only global geopotential model and a regional gravity field model updated in this study. First, we have constructed a regional gravity field model for Japan using updated gravity datasets together with a residual terrain model: 323,431 land gravity data, 77,389 shipborne marine gravity data, and Sandwell's v28.1 altimetry-derived global marine gravity model. Then, the geoid was determined with the gravity field model. The methodology for gravimetric geoid determination was based on the remove-compute-restore technique with Helmert's second method of condensation of topography (Stokes-Helmert scheme). Here, the hybrid Meissl-Molodensky modified spheroidal Stokes kernel was employed to minimize the truncation error under an appropriate combination of different kinds of gravity data. In addition, a high-resolution GSI-DEM on a 0.4 × 0.4 arc-second (10 m) grid, together with the SRTM-DEM on a 7.5 × 11.25 arc-second (250 m) grid, was utilized for precisely applying terrain correction to the regional gravity field model. Consequently, we created a gravimetric geoid model for Japan, consistent with 971 GNSS/leveling geoid heights distributed over the four main islands of Japan with a standard deviation of 5.7 cm, showing a considerable improvement by 2.3 cm over the previous model (JGEOID2008). However, there remain some areas with large discrepancies between the computed and GNSS/leveling geoid heights in northern Japan (Hokkaido), mountainous areas in central Japan, and some coastal regions. Since terrestrial gravity data are especially sparse in these areas, we speculated that the largeness of the geoid discrepancies there could be partly attributed to the insufficient coverage and accuracy of gravity data. The Geospatial Information Authority of Japan has started airborne gravity surveys to be covered over the Japanese Islands, and in future, we plan to develop a geoid model for Japan further accurately by incorporating airborne gravity data to come.

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Improvement of the geoid model over Japan using integral formulae and combination of GGMs

Cited by 6 publications

References 14 publications

Comparison of Helmert and rigorous orthometric heights over Japan

Comparison of Helmert and rigorous orthometric heights over Japan

Recovery of orthometric heights from ellipsoidal heights using offsets method over Japan

Refinement of a gravimetric geoid model for Japan using GOCE and an updated regional gravity field model

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