I have an interest in celestial navigation (CN). In CN we obtain a figure called the Greenwich Hour Angle (GHA) which is the number of degrees a navigational body, such as the Sun, is West of Greenwich at any particular moment in time based on GMT (Greenwich Mean Time)…or UT1. The GHA is never more than 360°.
It would be nice to be able to show someone a chart/map of the GHA as viewed from the South Pole (and showing Antarctica for reference) with the degrees around the “horizon” increasing in value Westward from Greenwich, crossing the IDL at 180° and finally returning to The Prime Meridian. It would be like a compass rose but the degree values would be increasing counter-clockwise as viewed from the South Pole.
Below is the code I use to show Antarctica but the degrees around the periphery provide East and West meridians.
gmt pscoast -Rg -JG-00/-90/7i -B15g15 -Dc -A5000 -Gblack -P > GMT_orthographic.ps
Any idea how I can do this with GMT v 5.4.3?
As always…thank you,