Earth at night
Import NASA's Night on Earth and Reproject in Polar Sterographic
This micro-tutorial requires GRASS 6.5
Get data
Download http://veimages.gsfc.nasa.gov//1438/land_ocean_ice_lights_8192.tif from http://visibleearth.nasa.gov/view_detail.php?id=1438
Import
# create simple XY location r.in.gdal in=land_ocean_ice_lights_8192.tif out=land_ocean_ice_lights for BAND in red green blue ; do r.region map=land_ocean_ice_lights.$BAND n=90 s=-90 w=-180 e=180 done #FIXME #hack PROJ WIND and cellhd to be 3 not 0 #run g.setproj to set datum == wgs84 and create PROJ_INFO etc. # now this location is lat/lon g.region n=90 s=45 w=-180 e=180 v.mkgrid map=grid_15 box=15,15 grid=12,24 pos=coor coor=-180,-90 breaks=30 v.mkgrid map=grid_30 box=30,30 grid=6,12 pos=coor coor=-180,-90 breaks=30
Reproject North side
#### NORTHERN HEMISPHERE #################
#create new loc'n based on epsg #3413
# WGS 84 / NSIDC Sea Ice Polar Stereographic North
# <3413> +proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs <>
# pull in grids
v.proj in=grid_15 location=xy_to_ll
v.proj in=grid_30 location=xy_to_ll
g.region n=10000000 s=-10000000 w=-10000000 e=10000000 res=5000 -p
MAP=land_ocean_ice_lights
for BAND in red green blue ; do
echo "Processing [$BAND] ..."
r.proj -n in=$MAP.$BAND location=xy_to_ll \
method=cubic_f memory=600
r.mapcalc "${MAP}_$BAND = if($MAP.$BAND > 255, 255, if($MAP.$BAND < 0, 0, int($MAP.$BAND)))"
g.remove "$MAP.$BAND"
g.rename "${MAP}_$BAND,$MAP.$BAND"
r.colors $MAP.$BAND color=grey255
echo
done
d.erase
d.rgb r=$MAP.red g=$MAP.green b=$MAP.blue
d.vect grid_15 type=boundary color=80:40:40
d.vect grid_30 type=boundary color=120:50:50
d.out.file night_on_earth_N -c size=1000,1000 format=png
d.out.file night_on_earth_N_small -c size=250,250 format=png
Reproject South side
#### SOUTHERN HEMISPHERE #################
#create new loc'n based on inverse of epsg #3413
#proj : stere
#datum : wgs84
#lat_0 : 90
#lat_ts : 70
#lon_0 : +135
#k : 1
v.proj in=grid_15 location=xy_to_ll
v.proj in=grid_30 location=xy_to_ll
g.region n=10000000 s=-10000000 w=-10000000 e=10000000 res=5000 -p
MAP=land_ocean_ice_lights
for BAND in red green blue ; do
echo "Processing [$BAND] ..."
r.proj -n in=$MAP.$BAND location=xy_to_ll \
method=cubic_f memory=600
r.mapcalc "${MAP}_$BAND = if($MAP.$BAND > 255, 255, if($MAP.$BAND < 0, 0, int($MAP.$BAND)))"
g.remove "$MAP.$BAND"
g.rename "${MAP}_$BAND,$MAP.$BAND"
r.colors $MAP.$BAND color=grey255
echo
done
# remove stray NULLs
for BAND in green blue ; do
echo "Processing [$BAND] ..."
g.rename "$MAP.$BAND,$MAP.$BAND.tmp1"
r.neighbors in="$MAP.$BAND.tmp1" out="$MAP.$BAND.tmp2"
r.patch in="$MAP.$BAND.tmp1,$MAP.$BAND.tmp2" out="$MAP.$BAND"
g.remove "$MAP.$BAND.tmp1,$MAP.$BAND.tmp2"
echo
done
d.erase
d.rgb r=$MAP.red g=$MAP.green b=$MAP.blue
d.vect grid_15 type=boundary color=80:40:40
d.vect grid_30 type=boundary color=120:50:50
d.out.file night_on_earth_S -c size=1000,1000 format=png
d.out.file night_on_earth_S_small -c size=250,250 format=png
