function sphere_to_xyz, coord, degrees=degrees ; $Id: sphere_to_xyz.pro 7092 2010-01-12 20:18:45Z jimm $ ;; Convert from lat/lon to xyz coordinates. lat/lon is radius, ;; lattitude, longitude. ;; Unfortunately, the function is misnamed since it does not use ;; spherical coordinates (i.e., radius, longitude, co-lattitude). ; coord = 3xN array of (r,lat,phi) ; R is radius. ; lat (lattitude) is the angle from the x,y plane (equator) toward +z ; Phi is measured from +x towards the +y in the equator. ; output = 3xN array of (x,y,z) if (size(coord))(1) ne 3 then $ message, 'Argument must have first dimension size equal to 3' r = coord(0, *) if keyword_set(degrees) then begin lat = coord(1, *)*!dtor phi = coord(2, *)*!dtor endif else begin lat = coord(1, *) phi = coord(2, *) endelse z = r*sin(lat) x = cos(phi)*r*cos(lat) y = sin(phi)*r*cos(lat) return, [x, y, z] end