[PROJ] Fwd: some help with cm-level GRS80 to WGS-84 transformation?

[Joseph Boardman]

-------- Forwarded Message --------
Subject: 	some help with cm-level GRS80 to WGS-84 transformation?
Date: 	Wed, 19 Jan 2022 11:28:24 -0700
From: 	Joseph Boardman <boardman at aigllc.com>
To: 	proj at lists.osgeo.org



Dear Proj Experts,

I'm a remote sensing geophysicist with experience in geodesy and mapping.

Right now I'm struggling trying to get a high-accuracy proj command to 
convert from GRS80 to WGS-84 at the cm level.

Any clues? cs2cs is not doing it.

cs2cs +proj=lonlat +ellps=WGS84 +to +proj=lonlat +ellps=GRS80 -d 8
-120 40
-120.00000000 40.00000000 0.00000000

Do I need to do a transformation pipeline per the 8.2.1 docs and use a 
Helmert transform? Any help much appreciated.

Best,

Joe

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