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

[Brian Shaw]

All

For anyone interested in learning more about the different realizations 
of WGS84 and deriving transformations between the various realizations 
of WGS 84 here is information for this article from the ASCE Journal of 
Survey Engineering.

*Kelly, K. M.* and Dennis, M. L. (2022). Transforming between WGS84 
realizations. /Journal of Surveying Engineering/, 148(2). doi: 
10.1061/(ASCE)SU.1943-5428.0000389 
<https://doi.org/10.1061/(ASCE)SU.1943-5428.0000389>

If interested email me and I can share.

Cheers
Brian

On 1/19/2022 4:06 PM, Greg Troxel wrote:
> Kirk Waters - NOAA Federal via PROJ <proj at lists.osgeo.org> writes:
>
>> I'm sure others with more experience will jump in, but I think the main
>> issue here is that WGS84 is a family of reference frames that are all based
>> on the GRS80 ellipsoid. So, the problem doesn't exactly make sense and the
>> various realizations of WGS84 differ at the cm level. Are you perhaps
>> trying to go from a NAD83 realization (such as NAD83(2011)) to a WGS84
>> realization (maybe ITRF14
>> or something)?
> I think Kirk has it exactly right.
>
> Also, GRS80 is not a datum, but only a name for an ellipsoid.  So
> "converting from GRS80" does not make sense.
>
>
> Further into the weeds, WGS84 realizations are dynamic datums and if you
> are talking about coordinates of crust-fixed objects you need to pay
> attention to epoch.  If you care about a few cm, you really need to pay
> attention.
>
> _______________________________________________
> PROJ mailing list
> PROJ at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/proj

-- 
*************************************
Brian Shaw
Rocky Mountain Regional Advisor (CO, MT, WY)
NOAA's National Geodetic Survey (NGS)
Cell Phone # 240-988-6363

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20220119/5e3b0965/attachment.html>