Jekeli, Christopher
(Division of Geodetic Science, School of Earth Science, Ohio State University)
,
Yang, Hyo Jin
(Division of Geodetic Science, School of Earth Science, Ohio State University)
,
Kwon, Jay Hyoun
(Dept. of Geoinformatics, University of Seoul)
The determination of the geoid in South Korea is a national imperative for the modernization of height datums, specifically the orthometric height and the dynamic height, that are used to monitor hydrological systems and environments with accuracy and easy revision, if necessary. The geometric heigh...
The determination of the geoid in South Korea is a national imperative for the modernization of height datums, specifically the orthometric height and the dynamic height, that are used to monitor hydrological systems and environments with accuracy and easy revision, if necessary. The geometric heights above a reference ellipsoid, routinely obtained by GPS, lead immediately to vertical control with respect to the geoid for hydrological purposes if the geoid height above the ellipsoid is known accurately. The geoid height is determined from gravimetric data, traditionally ground data, but in recent times also from airborne data. This paper illustrates the basic concepts for combining these two types of data and gives a preliminary performance assessment of either set or their combination for the determination of the geoid in South Korea. It is shown that the most critical aspect of the combination is the gravitational effect of the topographic masses above the geoid, which, if not properly taken into account, introduces a significant bias of about 8 mgal in the gravity anomalies, and which can lead to geoid height bias errors of up to 10 cm. It is further confirmed and concluded that achieving better than 5 cm precision in geoid heights from gravimetry remains a challenge that can be surmounted only with the proper combination of terrestrial and airborne data, thus realizing higher data resolution over most of South Korea than currently available solely from the airborne data.
The determination of the geoid in South Korea is a national imperative for the modernization of height datums, specifically the orthometric height and the dynamic height, that are used to monitor hydrological systems and environments with accuracy and easy revision, if necessary. The geometric heights above a reference ellipsoid, routinely obtained by GPS, lead immediately to vertical control with respect to the geoid for hydrological purposes if the geoid height above the ellipsoid is known accurately. The geoid height is determined from gravimetric data, traditionally ground data, but in recent times also from airborne data. This paper illustrates the basic concepts for combining these two types of data and gives a preliminary performance assessment of either set or their combination for the determination of the geoid in South Korea. It is shown that the most critical aspect of the combination is the gravitational effect of the topographic masses above the geoid, which, if not properly taken into account, introduces a significant bias of about 8 mgal in the gravity anomalies, and which can lead to geoid height bias errors of up to 10 cm. It is further confirmed and concluded that achieving better than 5 cm precision in geoid heights from gravimetry remains a challenge that can be surmounted only with the proper combination of terrestrial and airborne data, thus realizing higher data resolution over most of South Korea than currently available solely from the airborne data.
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제안 방법
For each resolution, the Bouguer anomalies were computed at the given terrestrial and airborne data points using a 30" -resolution topographic model derived from the Shuttle Radar Topography Mission (SRTM, Farr et al., 2007) and subsequently averaged over each of the common grid cells (as enumerated in Table 1).
Accounting for this through the Bouguer reduction practically eliminates the bias and improves the geoid determination. Further improvements are anticipated and being investigated with proposed methods to apply more rigorous downward continuation to the geoid of the terrestrial and especially the airborne Bouguer anomalies.
In this paper, we briefly review the geoid height determination from gravimetric data, discuss the basic concepts of computing the terrain effect, and on the basis of a quantitative assessment propose methods to combine the terrestrial and airborne data. This appraisal includes a preliminary analysis of the subsequent geoid height errors, which also confirms that the available combined gravimetric data have not yet reached the resolution and accuracy needed to obtain better than 5 cm accuracy in the geoid height.
성능/효과
In this paper, we briefly review the geoid height determination from gravimetric data, discuss the basic concepts of computing the terrain effect, and on the basis of a quantitative assessment propose methods to combine the terrestrial and airborne data. This appraisal includes a preliminary analysis of the subsequent geoid height errors, which also confirms that the available combined gravimetric data have not yet reached the resolution and accuracy needed to obtain better than 5 cm accuracy in the geoid height.
후속연구
In cells that are common to the terrestrial and airborne data sets, the values were combined by simple averaging. Downward continuation was performed only on the airborne free-air anomaly, as an option, since the downward continuation of the Bouguer anomalies requires further study. Helmert anomalies were obtained finally using the same SRTM terrain model, according to equation (10).
참고문헌 (21)
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