Since 1986 the National Geodetic Survy (NGS) has been adjusting NAD-83 nationwide by using GPS. This project, known as HARN (High Accuracy Reference Network), has established around 70 new stations in Arkansas. The stations, A-Order (1:10,000,000) and B-Order (1:1,000,000) are now available for use. The web site at the Center for Advanced Spatial Technologies contains a listing of all such stations in the state. (http://cast.uark.edu/cast/projects/gps/harn.html)

Until NGS completes its readjustment of the existing NAD-83 network in Arkansas for all stations, there will be TWO networks in the state. DO NOT MIX THE TWO!!!

If you are working with existing data, then you will want to use the superseded control to work with your data.

The readjustment process is expected to take two years to complete. At present the two different networks can have as much as 20 - 50 cm difference.

Being a NGS HARN position, Station ROUCH has already been given its updated positon. Other stations not in the HARN network have not been given their adjusted reference position. Stations such as the Center for Advanced Spatial Technologies (CAST) and the University of Arkansas at Monticello were not included in the HARN network and, as such, will remain on the previous NAD-83 configuration.

We still have the Superseded Survey Control position on this site if you wish to utilize the older position of this station. It can be found at:

http://argis.ualr.edu/rouchinfo.txt

Please note that the NGS does not recommend the use of superseded values for survey control.

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UNIVERSITY OF ARKANSAS AT LITTLE ROCK