[PROJ] Consistency of Proj and Esri transformations

[Brian Shaw]

Hi Dave

At this time NGS does not have a specific set of test parameters for 
datum transformations inside the US but that is something we are working 
on developing when the National Spatial Reference System is modernized 
in the near future.

You do not specifically mention US coordinates and transformations but 
if you are referring to transformations in the US there are occasionally 
issues with transformations not being up to date but you can compare 
results from Esri and PROJ with the NGS Coordinate Conversion and 
Transformation Tool (NCAT) to get an idea of any differences.

NGS recently updated the official transformations for the US with grids 
in NADCON 5 and VERTCON 3 that are both implemented in NCAT and changed 
a number of things that would impact other transformation software.  To 
have access to these transformations in Esri you have to download a 
special Coordinate System Data (CSD) package and install it for ArcGIS 
Desktop or ArcGIS Pro (two different packages depending on the 
software).  I do not believe the PROJ has implemented these 
transformations since NGS has not gotten them all registered with EPSG 
since it was a significant change from previous versions.  We are hoping 
to get this done sometime soon and I believe they have been updated in 
the ISO Geodetic Registry.

Here are links to a couple publications that may be of interest.

NADCON 5.0
https://geodesy.noaa.gov/library/pdfs/NOAA_TM_NOS_NGS_0081.pdf

VERTCON 3.0
https://geodesy.noaa.gov/library/pdfs/NOAA_TR_NOS_NGS_0068.pdf

If you are not referring to transformations in the US then please 
disregard all of the above.

Cheers
Brian

On 12/17/2021 10:08 AM, Dave Knopp wrote:
> Hey All,
>
> Does anyone have pointers to systematic comparisons, evaluations, or any
> consistency efforts re: numeric consistency between Proj transformation
> results and those produced via Esri projection engine?
>
> A second question: in the case of differences, any thoughts which should
> be adopted as a practical reference?
>
> Dave
> _______________________________________________
> 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