"South boundary cannot be < 0 for north polar orthographic projection (reset to 0)" ???
Using the command
pscoast -JG0/90/20 -Rg -B15g15 -Di -A5000 -W1 -P I get the warning used as subject in this thread. As the warning is not quite clear to me I would highly appreciate if someone could give me some deeper insight so that I can get ride of it.
It is just a warning. You are using an azimuthal projection centre in the north pole (-JG0/*90*/20). So the region cannot include the southern hermisphere and you are using -Rd which indicates the whole world (0/360/*-90*/90). So GMT reset the southern boundary to 0 (0/360/*0*/90).