Review lat/lon iterator for rotated reduced Gaussian grids

[sandorkertesz]

What happened?

Getting the lat/lons for a reduced_rotated_gg grid has been fixed in ecCodes 2.35.0. See ECC-1781 on https://confluence.ecmwf.int/display/ECC/ecCodes+version+2.35.0+released

This means that the code providing a workaround in GribField.grid_points() and GribField.grid_points_raw() should be reviewed.

Let's use the following example, retrieved from MARS with:

class=od,
stream=oper,
expver=1,
type=an,
date=20220101,
time=0,
area=28/0/-14/40,
grid=N320,
levtype=sfc,
param=167,
rotation=-22/-40,
target='rotated_N320.grib'

With ecCodes 2.35.0 I get the correct lat/lons:

grib_get_data rotated_N320.grib | more
Latitude Longitude Value
   84.037  140.000 2.4506007385e+02
   84.031  137.345 2.4494288635e+02
   84.011  134.702 2.4485694885e+02
   83.977  132.083 2.4484132385e+02
   83.931  129.500 2.4473585510e+02

but the key iteratorDisableUnrotate is still not available. So grid_points incorrectly calls unrotate:

def grid_points(self):
        import numpy as np

        if self.rotated and not self.rotated_iterator:
            warnings.warn(f"ecCodes does not support rotated iterator for {self.grid_type}")
            return self.grid_points_unrotated()

What are the steps to reproduce the bug?

See above

Version

latest

Platform (OS and architecture)

all

Relevant log output

No response

Accompanying data

No response

Organisation

ECMWF