I have a raster layer that I want to crop to a hemisphere centered on 30°N, 100°W, to use in an orthographic projection map. What is the best way to do this?
There doesn't seem to be an easy way to generate a hemisphere polygon to mask it by (which I'd think would be the obvious solution).
(Note that, unlike the question this is marked a duplicate of, this is asking about raster layers; the solutions presented in that question are for vector layers and do not work here.)
Similar to my answer in Where did the polygons go after projecting a map in QGIS? you can convert a WGS84 raster of bluemarble to an ortho projection with this command:
gdalwarp -overwrite -dstnodata 0 -ot Byte -s_srs "+proj=longlat +R=6371000" -t_srs "+proj=ortho +lat_0=30 +lon_0=-100 +x_0=0 +y_0=0 +R=6371000 +units=m +no_defs" -ts 6476 6476 -of GTiff -wo SOURCE_EXTRA=500 bluemarble.tif bluemarble-ortho.tif
The result looks like this:
You get a small artefact at the 180° meridian.
