function xyz_to_sphere, rect, degrees=degrees ; $Id: xyz_to_sphere.pro 7092 2010-01-12 20:18:45Z jimm $ ;; Convert from xyz to lat/lon coordinates which are raidus, ;; lattitude, longitude. ;; Unfortunately, the function is misnamed since it does not compute ;; spherical coordinates (i.e., radius, longitude, co-lattitude). ; rect = 3xN array of (x,y,z) ; output = 3xN array of (r,lat,phi) ; R is radius. ; lat is the lattitude: the angle from the x,y plane (equator) toward +z ; Phi is the longitude angle: measured from +x towards the +y in the equator. ; angles are in radians. x = rect(0, *) y = rect(1, *) z = rect(2, *) phi = atan(y, x) lat = atan(z, sqrt(x^2+y^2)) r = sqrt(x^2+y^2+z^2) if keyword_set(degrees) then begin return, [r, lat*!radeg, phi*!radeg] endif return, [r, lat, phi] end