[GRASS-user] Reprojecting to x,y grid

[Ken Mankoff]

Hello,

On 2020-11-17 at 10:06 -08, Ken Mankoff <mankoff at gmail.com> wrote...
> I've successfully worked in rotated pole coordinates (e.g., [1]) but
> because I don't know what (x,y) coord contains the pole, I haven't
> figured out how to adapt this to the rotated pole situation as in [1].
> Anyway, this isn't a rotated pole...

I was incorrect - this is a rotated pole coordinate system.

When I run the following code on GRASS 7.4, I get the attached graphic. The key part here is that the rotated pole is at (lon,lat) = (-200,18).



grass -c EPSG:4326 Gnorm

# Import something into the normal location
v.import input=~/data/Zwally_2012/sectors output=Z

cat << EOF > ./Gnorm/PERMANENT/PROJ_INFO
name: General Oblique Transformation
datum: wgs84
towgs84: 0.000,0.000,0.000
proj: ob_tran
o_proj: latlon
ellps: wgs84
a: 6378137.0000000000
es: 0.0066943800
f: 298.2572235630
lat_0: 0.0000000000
lon_0: 180.0000000000
o_lat_p: 18.0
o_lon_p: -200.0
EOF

# rotated_pole:grid_north_pole_latitude = 18. ;
# rotated_pole:grid_north_pole_longitude = -200.

cat << EOF > ./Gnorm/PERMANENT/PROJ_UNITS
unit: degree
units: degrees
meters: .0174532925
EOF

grass -e -c EPSG:4326 Grot
grass ./Grot/PERMANENT

v.proj location=Gnorm input=Z
g.region vector=Z

d.mon start=wx0
d.vect Z
d.grid 1:0:0


The above code run in GRASS 7.4.0 on a clean Ubuntu 18.04 VM produces the attached graphic. However, when I run the exact same code in GRASS 7.8.4 it does not work. The reproject/rotate does not occur, and Greenland remains at 62-82 N, and 22-72 W.

The contents of the "Gnorm" folders is appears identical. The md5sum of DEFAULT_WIND, MYNAME, PROJ_EPSG, PROJ_INFO, and PROJ_UNITS are all the same.

I can do the work in GRASS 7.4 in a VM but I'd prefer to do it on the main development machine in the latest GRASS. Does anyone have any idea why this feature stopped working?

Thanks,

  -k.
  

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