[BUG] d.grid does not display grids properly near the poles in polar projections

[mankoff]

d.grid does not display grids properly near the poles in polar projections

Mailing list discussion: https://lists.osgeo.org/pipermail/grass-user/2020-December/082021.html

grass -c epsg:3995 ./G_N
g.region n=2930000 s=-2500000 w=-4250000 e=4310000 nsres=10000 ewres=10000 -pa
d.mon wx0
d.grid -g 1:0

Including a sea ice basemap for context the above command generates this graphic:

If a grid is generated in EPSG:4326 and then imported (via v.proj) to the polar projection, then it works:

grass -c EPSG:4326 ./G_tmp_4326
g.region e=180 w=-180 s=-90 n=90 res=1 -pa
v.mkgrid grid=36,18 map=grid_10deg
exit

v.proj location=G_tmp_4326 input=grid_10deg
d.vect grid_10deg fill_color=none color=cyan

Oddly, if the exact same commands are run but the polar projection is EPSG:3413 instead of EPSG:3995, then a gap exists in the grid:

rm -fR G_tmp G_tmp_4326

grass -c epsg:3413 ./G_tmp
g.region n=2930000 s=-2500000 w=-4250000 e=4310000 nsres=10000 ewres=10000 -pa
r.import input=/home/kdm/projects/knit/map/data/N_197909_extent_v3.0.tif output=seaice
d.mon wx0
d.rast seaice
d.grid -g 10:0 color=red

grass -c EPSG:4326 ./G_tmp_4326
g.region e=180 w=-180 s=-90 n=90 res=1 -pa
v.mkgrid grid=36,18 map=grid_10deg
exit

v.proj location=G_tmp_4326 input=grid_10deg
d.vect grid_10deg fill_color=none color=cyan

rm -fR G_tmp G_tmp_4326

• Operating System: Kubuntu 20.04
• GRASS GIS version 7.8.4

version=7.8.4
date=2020
revision=exported
build_date=2020-12-19
build_platform=x86_64-pc-linux-gnu
build_off_t_size=8
libgis_revision=2020-12-19T12:38:20+00:00
libgis_date=2020-12-19T12:38:20+00:00
proj=7.2.0
gdal=3.2.0
geos=3.9.0
sqlite=3.31.1