[PROJ] How to apply Helmert trafo

[Fabian Gross]

Dear proj-members,

I would like to apply a Helmert trafo as part of a datum shift.
The example follows the EPSG geomatics guidance 7/2 (report 373-7-2):

>From WGS72 (4984) -> WGS84 (4978).

There are 2 issues:
1. How to apply Helmert-Trafo? I.e. 
with or 
without the push/pop of the ellipsoidal height. 
Only if it is not pushed/popped do the values fit to the reference and the 
direct/naive implementation of Helmert.
2. The scale parameters in the example (0.219) and the EPSG catalogue of 
pyproj (0.2263)  do not agree.

The attached file has the test case.


Kind regards

Fabian Gross
Telefon +49 (711) 648 71-995
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