Geoid 12A Problems ?

> Ok So I processed GPS Static data for a point I did a network RTK solution on using Geoid 09 and then downloaded processed the static data using 2 local CORS stations in Topcon Tools .
> Side note : Topcon Tools will go out and get you the closest CORS rinex data for the observation and download it into the program . Very nice seems to be a little more accurate than OPUS .
>
> Back to the subject . So I use Geoid 09 to process the data and it matches the Network RTK with in hundreths all the way around , all good.
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> So I download the new 12A Geoid and process the data in a totally new job and get 0.78 higher elevation .
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> What is going on. This is going to create many headaches .

wild guess. in MD there is approx 0.7' difference in elevation betwixt NGVD 29 and NAVD 88. you might want to check datums first...NC to MD might be similar in vertical offset

Make sure you have the antenna offset setting correctly entered in both OPUS and your dataColletor for network rtk use. The Topcon GR-3 offset is real close to 0.78' and I would bet GR-5 is close to that too. Was it high or LOW?

Everything set correct . The only difference is the geoid . The 07 static matched the 07 vrs . 12 static off .

GEOID09 works with NSRS2007 / CORS96 ellipsoid heights, GEOID12 and 12A work with NAD83(2011) ellipsoid heights, if you are using GEOID12 in an absolute sense, then you must use NAD83(2011) ellipsoid heights. I am guessing the problem revolves around the ellipsoid heights in use. Both methods should give you close to the same orthometric heights.

In addition to that, ALL processing with NAD83(2011) should be using the new absolute antenna models and previous realizations should use the older antenna models, most software supported the old relative antenna models.

You can't just mix and match or change one piece of the puzzle and expect to get the same answers.

EDIT to add, did you check the automaticly imported position of the CORS in Topcon Tools before processing?

SHG

At the point what's the difference between Geoid09 and Geoid12 heights?

The difference in Geoid09 and Geoid12 at Cors station DOB was .01'
and .05' for Cors station NCNW .
The orthometric difference as computed by Topcon tools was .7' at the site . I suspect I am mixing apples and oranges somewere .
I am working on getting the nad 83 2007 ellipsoid heights to compare to the nad 83 2011 ellipsoid heights but the NGS web site is not working well today . Still even if I was using Nad83(2011) coords with either Geiod I cannot see .7' coming into play . I was just testing the difference since we are moving over to nad 83(2011) .

I wish they would stop screwing with the coordinates .

What geoid was used to collect the RTK position?

I suspect I am mixing apples and oranges somewere .

It sounds like it; somewhere. But it may not be you that's doing it. It could be somewhere in the software.

Since there is almost no difference between the ellipsoid heights and the Geoid heights the .7' shouldn't show up.

I did two VRS observations , once Dec when NC was still on nad83 (2007) with Geoid 09 .
Then on the new NAD 83 (2011) with Geoid 09 .
I just wanted to see if there was a big change and no same. What I did not do was load Geoid 12 into the data collector and check the difference on the new VRS .

I did a static to check this , So maybe the differnce is the Ellipsoid hieghts based on 2007 to 2012.

Went out today did a VRS with nad83 geoid 12a matched the old nad83 Geiod 09 VRS observations , a Opus solution , and my own processed cors observation with in expected tolerances .

Appears topcon tools is doing something strange will keep digging.