National Adjustment of 2011 – What Does it Mean For You?

National Geodetic Survey

The National Geodetic Survey (NGS) has been working for over a year now to adjust the NAD83 datum with what is called the National Adjustment of 2011 or NA2011. How much adjustment are we talking about here? If you guessed only about two centimeters, you would be right on the money.

So why are the NGS geodesists working so hard for such a small change and is it worth the potential problems it could cause users of NAD83? It turns out the reasoning behind the adjustments are sound and will be a benefit to the future of surveying and GPS usage.

The main advantage of the NA2011 is that it will tie together and align passive(in ground monuments) and active(CORS) control stations throughout the United States. There are roughly 80,000 passive control marks that will be effectively brought into the modern system.

It is important to remember that this is not a new datum (that will be coming in about ten years); It is an adjustment of the current NAD83 datum. However, there will be a new geoid model (Geoid12) as a result of the changes. Of course this new hybrid geoid will not be developed until after the NA2011.

Fun stuff! The projected completion date for the adjustment is June 30, 2012 so it could be just around the corner. Of course they had originally planned on completing it before the end of 2011 but maybe this time they will be on schedule. If you want more information about the NA2011 you can visit the NGS web site.

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