NAD 1983 or NA 2011 ?

You should use GEOID12a with 2011, and there are differences. Am I misunderstanding the question? Not sure what regions have to do with it, but the differences are greater in different regions.

For instance, the coast here changes relatively quickly.

When switching between nad1983 and nad1983(2011) I have a vertical shift of 4' on stored points. I just found out that our local RTK network does not transmit corrections with the 2011 adjustment yet. Thanks

I have found that, as the NGS suggests, 2011 and 12a were made for each other, and should be monogamous.

Hi there,

You indicate that you are seeing a vertical shift of four (4) feet between points expressed in NAD83 and NAD83(2011). This brings to mind a few questions.

1. What type of heights? If you are finding this magnitude of difference in ellipsoid heights, I would be surprised. See the following links:

http://www.ngs.noaa.gov/CORS/coord_info/myear_FAQ.shtml#CoordDiff

2. If you are referring to orthometric heights (NAVD 83), the issue becomes how the ellipsoid height is transformed into an orthometric heights. This process involves the use of a model of the geoid-ellipsoid separation. An NAD83 ellipsoid height is used in combination with the GEOID2012A model to approximate an NAVD 88 height.

3. I have seen instances where users used ITRF (or WGS 84) coordinates considering them equivalent to NAD83. They are not. In fact, depending on where you are in the US there are greater than meter-level differences in ellipsoid heights between ITRF and NAD83.

4. On the matter of NAD 83 there are a number of implementations. In short, there was the original implementation NAD83(1986), HARN versions done on a state-by-state basis, an ellipsoid height modernization versions likewise done state-by-state, then the national adjustments of 2007 and 2011. Keeping these straight requires careful attention. The links in 1 above show the magnitude of differences between the most recent versions of NAD83. The difference between NAD83(1986) and the HARN versions are the greatest magnitude.

5. For the expected magnitudes of differences between versions of NAD 83 see NADCON or GEOCON.

6. If you are basing your work on a single point, it could be in error.

For additional excruciating details, see: http://geodesyattamucc.pbworks.com/w/page/13931102/FrontPage#Class1418March2013HorizontaldatumsintheUSnbspNAD27/NAD831986/NAD83HARN/NAD832007

Good luck,

DMM

where is you? here's what i've noticed in central texas (specifically, the austin metro area)

ever since moving over to 11/12a i've been checking into almost every single municipal/county/NGO control monument i've found about 2-tenths high. 99% of those monuments were set using something prior to the 03 geoid.

I believe your problem is something other than the NAD83 realization and geoid model, granted you should be using NAD 83(2011) with Geoid12A, BUT a four foot shift indicates something else is going on, I would guess it has something to do with WGS84 and a transformation with one set of coordinates and not the other.

SHG

> When switching between nad1983 and nad1983(2011) I have a vertical shift of 4' on stored points. I just found out that our local RTK network does not transmit corrections with the 2011 adjustment yet. Thanks

I am having this same problem. I'm in nYC. I found the same 4 feet but between 2 different gps antennas. I'm thinking now maybe one of the collectors may be set to nad83 2011