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Control surveys
Author(s) -
Wade Elizabeth B.,
Zilkoski David B.
Publication year - 1987
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg025i005p00825
Subject(s) - geodetic datum , geodesy , very long baseline interferometry , geology , scale (ratio) , offset (computer science) , coordinate system , computer science , mathematics , geography , geometry , cartography , programming language
North American Datum (NAD 83) Readjustment Project. The new adjustment of the North American Datum of 1983 was completed in July 1986. A simultaneous mathematical adjustment of 250,000 stations was performed to eliminate distortions in the horizontal part of the National Geodetic Reference System (NGRS). The datum uses the Geodetic Reference System of 1980 (GRS 80) ellipsoid. The datum reference uses Doppler point positions for the definition of the earth's center of mass and Very Long Baseline Interferometry (VLBI) observations for the definition of scale and orientation. The parameters to be applied to Doppler X, Y, Z coordinates in the NWL 9D coordinate system to transform into the NAD 83 are: −0.811I″ rotation, −0.6 ppm scale, and + 4.5 meters Z offset. Datum transformation procedures are being developed to allow users to convert from NAD 27 to the NAD 83.