A comparison of recent Earth gravitational models with emphasis on their contribution in refining the gravity and geoid at continental or regional scale |
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Authors: | D N Arabelos C C Tscherning |
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Institution: | 1. Department of Geodesy and Surveying, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece 2. Niels Bohr Institute, University of Copenhagen, Juliane Maries vej. 32, 2100, Copenhagen Oe, Denmark
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Abstract: | Since the publication of the Earth gravitational model (EGM)96 considerable improvements in the observation techniques resulted
in the development of new improved models. The improvements are due to the availability of data from dedicated gravity mapping
missions (CHAMP, GRACE) and to the use of 5′ × 5′ terrestrial and altimetry derived gravity anomalies. It is expected that
the use of new EGMs will further contribute to the improvement of the resolution and accuracy of the gravity and geoid modeling
in continental and regional scale. To prove this numerically, three representative Earth gravitational models are used for
the reduction of several kinds of data related to the gravity field in different places of the Earth. The results of the reduction
are discussed regarding the corresponding covariance functions which might be used for modeling using the least squares collocation
method. The contribution of the EIGEN-GL04C model in most cases is comparable to that of EGM96. However, the big difference
is shown in the case of EGM2008, due not only to its quality but obviously to its high degree of expansion. Almost in all
cases the variance and the correlation length of the covariance functions of data reduced to this model up to its maximum
degree are only a few percentages of corresponding quantities of the same data reduced up to degree 360. Furthermore, the
mean value and the standard deviation of the reduced gravity anomalies in extended areas of the Earth such as Australia, Arctic
region, Scandinavia or the Canadian plains, vary between −1 and +1 and between 5 and 10 × 10−5 ms−2, respectively, reflecting the homogenization of the gravity field on a regional scale. This is very important in using least
squares collocation for regional applications. However, the distance to the first zero-value was in several cases much longer
than warranted by the high degree of the expansion. This is attributed to errors of medium wavelengths stemming from the lack
of, e.g., high-quality data in some area. |
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