Knowledge Base - Technical Articles

Technical Article   HowTo:  Determine which NAD_1983_To_WGS_1984 transformation to use

Article ID: 24159
Software:  ArcGIS - ArcEditor 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcInfo 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcView 9.2, 9.3, 10, 9.3.1 ArcGIS for Desktop Advanced 10.2, 10.1, 10.2.1, 10.3, 10.3.1, 10.1 SP1, 10.2.2 ArcGIS for Desktop Basic 10.2, 10.2.1, 10.3, 10.3.1, 10.2.2, 10.1, 10.1 SP1 ArcGIS for Desktop Standard 10.2.1, 10.1, 10.2, 10.1 SP1, 10.3.1, 10.2.2, 10.3
Platforms: N/A


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 and Pacific (for Hawaii, Guam, etc.) 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 became increasingly different.

Instructions provided help in determining the correct datum transformation to use when transforming data between the NAD 1983 and the WGS 1984 datums.


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.

  • Here is the list of supported Geographic Transformations between NAD 1983 and WGS 1984 at ArcGIS Desktop 10.3.1. Certain of these transformations may not be available at earlier version of the software. -show me-

    [O-Image] List of transformations
  • One of the most important considerations in selecting a geographic transformation is consistency: using the same transformation each time to transform between these two Geographic Coordinate Systems (datums). When using the Project Tool, the transformation method applied is recorded in the metadata.
  • The EPSG database can be downloaded from the similarly titled link in the Related Information section below. This database is a free download and is updated frequently. This database includes information on the source of datum transformation parameters and may include the accuracy of the transformation from the transformation source.

     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.

     Information from new versions of the EPSG database are not automatically added to the Projection Engine. New items are added when requested by users.

  • The difference between the GRS 1980 spheroid, the basis for the NAD 1983 datum, and the WGS 1984 spheroid is 0.0001 meters in the length of the semi-minor axis - the distance between the geodetic center of the earth and the North Pole. The semi-minor axis for GRS 1980 is 6356752.3141 meters. This axis for WGS 1984 is 6356752.3142 meters, while the semi-major axis both spheroids measures 6378137 meters.

Related Information

Created: 12/31/2002
Last Modified: 8/14/2015

Article Rating: (2)
If you would like to post a comment, please login


By TrevorGonskaNAU - 08/21/2013 3:50 PM

Great article! It helped a lot!

I dont understand why others are having difficulty understanding and applying the information in this article. I found it very helpful.


By Anonymous - 04/25/2011 9:50 AM

I followed the article’s instructions, but experienced another problem. I’ve provided details below.

I found this article in the HowTo section. It is *NOT* a How To. In order for it to be a How To, it needs to be re-written in user-friendly English. For example: "To determine which transformation method to use, first you need to determine which part of the globe you will be mapping. If you are mapping in the continental USA, then the most appropriate transformation is NAD_1983_To_WGS_1984_1. However, if you are mapping Hawaii, use... or if you are mapping Alaska use..." Something like that!


By Anonymous - 06/13/2007 12:03 PM

The article needs to be updated.

the article does not give any info for when transformations 2,3,6,7 & 8 might be most relevant.

By Anonymous - 06/13/2007 11:56 AM

The article needs to be updated.

the article says the information shown is only relevant up to arcgis v9.1, but does not tell users of v9.2 what to do or direct them where else they need to read if they have a similar question (like I do).

By Anonymous - 12/08/2006 10:34 AM

The article needs to be updated.

Hi there, this article is great, and served me well in 9.1. But in 9.2 it looks like there are now 8 different transformations to choose from. Which one to choose? Also, I'd love to hear about any other documentation available about projections/coordinate systems changes between 9.1 and 9.2 - especially since I'm teaching a class on it in February! thanks! Amanda Henley