Estonia (EST-GEOID2017)
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Authors: A. Ellmann, et al.
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Created: 2017
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Resp: A. Ellmann
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Description:
EST-GEOID2017 is a quasi-geoid model for Estonia, covering the region from 57°N to 60°N latitude and from 20°E to 30°E
longitude, with a spatial resolution of 1'x2'(that is about 1.8x1.8 km). It is referred to the GRS80 ellipsoid
(ETRF2000 frame, epoch 2000.0). It is based on land, sea-bottom, ship and airborne gravity data, with a spatial coverage
of 1 point per 10 km². The quasi-geoid determination is based on a least-squares modified Stokes formula, where long-wavelength
information comes from the GOCO05s global gravity model up to degree and order 200. The resulting gravimetric quasi-geoid (that
is called GRAV-GEOID2017) is fitted with 131 national GNSS/levelling observations. After removing a bias of about 56.1 cm, the
fitting procedure is performed by least-squares collocation. The post-fitting uncertainties of the resulting EST-GEOID2017 hybrid
model show a standard deviation of 4.2 mm, which is of the same level as the uncertainty of the used GNSS/levelling points. Note
also that due to the low elevations and the insignificant Bouguer gravity anomalies within the study region, the difference between
geoid and quasi-geoid models does not exceed 3 mm.
References:
A. Ellmann, S. Märdla, T. Oja (2019). The 5 mm geoid model for Estonia computed by the least squares modified Stokes formula.
Survey Review. DOI: 10.1080/00396265.2019.1583848
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