Hi Ken,
On Thu, Dec 31, 2020 at 3:06 AM Ken Mankoff <[email protected]>
wrote:
Dear GRASS List,
Can someone suggest what setup to use (EPSG code? proj4 code?) to
have the projection centered on the N. pole? I'm looking to create
a graphic similar to this image in the Raster Gallery:
https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgrass.osgeo.org%2F%2Fimages%2Fgallery%2Fraster%2Fday_on_earth_N.png&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=zcVbgCptTcrREvuVucAfEWdb%2BPH2Qsl6DktIkru94jE%3D&reserved=0
If I set up a polar projection based on
https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspatialreference.org%2Fref%2Fsr-org%2F8243%2F&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=QrsQH1MA6ehd%2BcPpLwwQ6190ki6shHnr7UptJsF50EU%3D&reserved=0
using:
grass -c ./G
g.proj -c proj4="+proj=stere +lat_0=90 +lat_ts=45 +lon_0=-170 +k=1
+x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
Things mostly work, but
d.grid -g 1:0 color=red
does not show latitude lines on most of the graphic (see attached).
I managed to generate it with
Preparation of a 10 degree grid:
# EPSG:4326
GRASS :~ > g.region -dp
projection: 3 (Latitude-Longitude)
zone: 0
datum: wgs84
ellipsoid: wgs84
north: 90N
south: 90S
west: 180W
east: 180E
nsres: 1
ewres: 1
rows: 180
cols: 360
cells: 64800
GRASS :~ > v.mkgrid grid=36,18 map=grid_10deg
# download "Natural Earth I with Shaded Relief, Water, and
Drainages"
from
https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.naturalearthdata.com%2Fdownloads%2F10m-raster-data%2F10m-natural-earth-1%2F&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=BmlSMFy8mUpdUQxbZw10dM7Rzzq4Vztpc33Ha8dx75M%3D&reserved=0
GRASS :~ > r.import in=NE1_HR_LC_SR_W_DR.tif
output=natural_earth_global_landcover
GRASS :~ > g.region raster=natural_earth_global_landcover.1
GRASS :~ > r.composite r=natural_earth_global_landcover.1
g=natural_earth_global_landcover.2
b=natural_earth_global_landcover.3
out=natural_earth_global_landcover.rgb
GRASS :~ > exit
# WGS 84 / Arctic Polar Stereographic
https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fepsg.io%2F3995&data=04%7C01%7Cjeir%40hi.is%7Cbab065ba5fa94867219a08d8ae786727%7C09fa5f0e211846568529677ed8fdbe78%7C0%7C0%7C637451179441104707%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=67g63WlKT3zJfzmTuPxNAciU9Uq65N%2F6ypc%2FpjntWT8%3D&reserved=0
grass78 -c epsg:3995 ~/grassdata/arctic_polar_stereographic
GRASS :~ > g.proj -w
PROJCS["WGS 84 / Arctic Polar Stereographic",
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4326"]],
PROJECTION["Polar_Stereographic"],
PARAMETER["latitude_of_origin",71],
PARAMETER["central_meridian",0],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["Easting",SOUTH],
AXIS["Northing",SOUTH],
AUTHORITY["EPSG","3995"]]
GRASS :~ > g.region n=2930000 s=-2500000 w=-4250000 e=4310000
nsres=10000 ewres=10000 -p
GRASS :~ > v.proj location=latlong_wgs84 mapset=PERMANENT
input=grid_10deg
GRASS :~ > r.proj location=latlong_wgs84 mapset=PERMANENT
input=natural_earth_global_landcover.rgb
GRASS :~ > d.mon wx0
GRASS :~ > d.rast natural_earth_global_landcover.rgb
GRASS :~ > d.vect grid_10deg type=boundary
The resulting map looks as attached (hope I didn't forget to copy a
command here).
Indeed, d.grid doesn't looks as expected
GRASS :~ > d.grid 10 -w
.. is incomplete. Worth a bug report, IMO.
Cheers,
Markus
-- Markus Neteler, PhD
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- free data with free software
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