[PROJ] ct2 format and grid_transformation.sql

Wed Sep 16 03:27:46 PDT 2020

I want to be clear on these things:

Am I right that ct2 format can not be described in grid_alternatives.sql/ grid_transformation.sql/ grid_transformation_custom.sql, because there is no EPSG code for ct2 format (NTv2 format (EPSG:9615)
and GTX format (EPSG:9665))?

I can only transform ct2 format into GTG and use in proj piplines directly and also in GDAL but not in transformations where EPSG code is involved, correct?

As today all grids should be in GTG format, but  in grid_alternatives.sql/ grid_transformation.sql/ grid_transformation_custom.sql  the names of the grid are with endings .gsb and .gtx, so that mean that where EPSG code is involved GTG will be transformed back into .gsb or .gtx grid formats to perform transformation in such an applicatios as QGIS and so on (where proj is in background and EPSG codes are involved in the transformation), correct?

>From here, I can see that I can convert ct2 format into GTG, but ct2 format grid can not be decribed in  grid_alternatives.sql/ grid_transformation.sql/ grid_transformation_custom.sql and can not be used in transformation involving EPSG codes, correct?
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