-
Changing Geoid with existing control network –Easy way..
So I have a data set of about 250 control points covering about a 60 mile corridor of highway that were processed using Geoid09 and I suspect were leveled through with a DiNi level. I need to convert them to Geoid12B.
Has anyone ever done this trough TBC by just changing the coordinate system? I will be able to run a DiNi level from at least two Vertical II monuments to spot check and handful for QA/QC. But if anyone knows a better (safer) way I am all ears…
-
3 Replies
-
If the elevations are determined by levelling why does a geoid model need to come into play?
-
I don’t understand the question? Hybrid geoid models are simply a mathematical model (N in H=h-N) between NAD83 ellipsoid heights and a gravimetric surface that is constrained (purposefully distorted) to NAVD88 leveled bench marks (orthometric heights). GEOID09 is coupled with the NAD83(NSRS2007) realization. GEOID12B is coupled with the NAD83(2011) realization. In is incorrect to pair them in any other way. Orthometric heights (H) don’t change, only ellipsoid heights (h) and geoid heights (N) change with each realization.
-
You have XYZ information you wish to fix with GEOID 12B applied.
Then create a file in TBC with the correct projection parameters and GEOID12B as the model. Export the control to a XYZ file, then simply import your XYZ file into the new TBC project.
This will “attach” Lat, Long, Ellipsoid height to the points.
You can also attempt to just update the existing file, I would be careful doing that, I’ve gotten some interesting results doing that across TSO, TGO and TBC. One thing that’s cool is there is the undo button.
Attaching GEOID12B to the current Ellipsoid height will change the Z value.
Log in to reply.