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| Titel |
Terrestrial Gravity Measurements towards Turkish Height System Modernization |
| VerfasserIn |
Mehmet Simav, Hasan Yıldız, Ahmet Direnc, Ali Türkezer |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083197
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| Zusammenfassung |
| One of the key components of the Turkish height system modernization project
is the determination of high resolution regional gravity field from terrestrial and
satellite measurements. Terrestrial gravity data in Turkey have been collected by
different organizations over many decades. Although the density of these data is
sufficient in most part of the country, the poor quality mainly due to the inconsistent
coordinate and gravity reference frames prevented us to compute a gravimetric geoid
model of a few cm accuracy. Therefore, we are now working on the elimination
of discrepancies between these historical datasets, developing a national gravity
database and preparing guidelines for measuring, reducing, processing and exchanging
terrestrial gravity data. In the meantime, new field campaigns were started in 2011 to
extend the national gravity standardization network and to increase the amount of
control points to be used for the quality check of the historical data. This study
describes the (i) recent relative gravity and vertical gravity gradient measurements,
(ii) numerical investigations on the standard reductions due to Earth tides, polar
motion, instrumental height and air pressure variations, (iii) applied adjustment
models and adjustment results. Preliminary results show that differences between
using Longman formula adopted in Scintrex CG3 and CG5 instruments and the
specific tide catalogues (e.g. Cartwright-Tayler, Tamura) with approximate amplitude
and phase-difference values for the main tide wave groups never exceed 5 μGal.
Maximum reduction for the pole motion is about 2 μGal. The variations in atmospheric
pressure lead to a maximum reduction of about 5 μGal. Vertical gravity gradient
values determined at 98 sites are in the range of -0.2078 to -0.4357 mgal/m with a
mean of -0.2995 mgal/m that is about 9 μGal/m different from the theoretical value. |
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