When originally defined, North American Datum 1983 (NAD 1983) and World Geodetic System 1984 (WGS 1984) were equivalent. In order to minimize coordinate changes, NAD 1983 is tied to the North American, Pacific (for Hawaii, Guam, etc.), and Marianas tectonic plates. WGS 1984 is tied to the International Terrestrial Reference System (ITRF) which is independent of the tectonic plates. Over time, the two coordinate systems have become increasingly different.The instructions provided should help in determining the correct geographic/datum transformation to use when transforming data between NAD 1983 and WGS 1984.
The accuracy of the transformations listed in this article are in meters. The accuracy values have been calculated by the organization that created each transformation. These values are provided as a convenience to users, but are not verified by Esri.
Note: ArcGIS Desktop version 9.2 uses information from version 6.10.2 of the database. Version 9.3 uses information from version 6.13. ArcGIS Desktop version 10.0 uses information from version 7.4. Version 10.3.1 utilizes information from 8.6.2.
Note: Information from new versions of the EPSG database are not automatically added to the Esri projection engine. New items are added when requested by users.
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