Hello,

I recently started to use Apache SIS. It was fairly easy to learn how to
convert between two coordinate systems. However, my application requires
the precision brought by the use of NADCON and NTV2 grid shifts.

I do see in the logs the following warnings when I perform a coordinate
conversion:

Oct 17, 2019 12:36:32 PM
org.apache.sis.referencing.operation.CoordinateOperationFinder
createOperations
WARNING: Can not parse “NTv2_0.gsb” as a file in the NTv2 format.
Oct 17, 2019 12:36:32 PM
org.apache.sis.referencing.operation.CoordinateOperationFinder
createOperations
WARNING: Can not parse “conus.las” as a file in the NADCON format.
Oct 17, 2019 12:36:33 PM
org.apache.sis.referencing.operation.CoordinateOperationFinder
createOperations
WARNING: Can not parse “NTv2_0.gsb” as a file in the NTv2 format.
Oct 17, 2019 12:36:33 PM
org.apache.sis.referencing.operation.CoordinateOperationFinder
createOperations
WARNING: Can not parse “conus.las” as a file in the NADCON format.

I do have a copy of all .las, .los and .gsb files. My first question is:
where does Apache SIS expect these files to be located?

The org.apache.sis.internal.referencing.provider.NADCON class only
references one grid (the conus grid, defined by conus.los and conus.las
files). How do I add other NADCON grids (ex: alaska) ? Should I modify the
code of the  NADCON class to take into account my other NADCON grid files ?

Same question for  org.apache.sis.internal.referencing.provider.NTv2. In
this particular case, it's not clear to me how to register my NTv2 files
since the NTv2 class uses identifiers like 9615 instead of file names. The
.gsb files I have are for Australia, Brazil, Canada, France, Germany
and Great Britain

Any guidance is appreciated,

-Thierry

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