X/Y axis units (radian)

[magau]

According with the NUWG NetCDF Conventions for naming units, the value "rad" for radian unit shouldn't be used. Instead, the correct value should be "radian".
As one can see in the end of the following document:
https://www.unidata.ucar.edu/software/netcdf/netcdf/Units.html

My proposal to resolve this issue is to add both values ("rad" and "radian") as possible value for the X/Y axis/coordinates unit, in order to keep retro-compatibility.

So, instead of:
else if( EQUAL( szUnits, "rad" ) )
I sugest:
else if( EQUAL( szUnits, "rad" ) || EQUAL( szUnits, "radian" ))

As far as I know the following two lines should be changed:

gdal/gdal/frmts/netcdf/netcdfdataset.cpp

Line 3642 in 9e00045

else if( EQUAL( szUnits, "rad" ) )

gdal/gdal/frmts/netcdf/netcdfdataset.cpp

Line 3660 in 9e00045

else if( EQUAL( szUnits, "rad" ) )

Hope this small change can improve the GDAL library in order to keep the NetCDF standard to be used correctly.

Cheers!

[rouault]

Are there datasets that use "radian" and you hit that issue ? Your proposed change is reasonable. You could issue a pull request with it.

[magau]

Yes. The geostationary projection requires X/Y axis values in radians or km. My objective here is to encourage the data providers to use de "radians" value for the "units" attribute if they choose to represent the coordinates in radians and stop using "rad" which is the units for "absorbed dose".

https://en.wikipedia.org/wiki/Rad_(unit)

[rouault]

Fixed per #1803