public subroutine limang(pos1, poso, alimb, afrac)
THIS FUNCTION DETERMINES THE ANGLE OF AN OBJECT ABOVE OR BELOW
THE EARTH'S LIMB (HORIZON). THE GEOMETRIC LIMB IS COMPUTED,
ASSUMING THE EARTH TO BE AN AIRLESS SPHERE (NO REFRACTION OR
OBLATENESS IS INCLUDED). THE OBSERVER CAN BE ON OR ABOVE THE
EARTH. FOR AN OBSERVER ON THE SURFACE OF THE EARTH, THIS
SUBROUTINE RETURNS THE APPROXIMATE UNREFRACTED ALTITUDE.
POS1 = POSITION VECTOR OF OBSERVED OBJECT, WITH RESPECT TO
ORIGIN AT GEOCENTER, COMPONENTS IN AU (IN)
POSO = POSITION VECTOR OF OBSERVER, WITH RESPECT TO ORIGIN
AT GEOCENTER, COMPONENTS IN AU (IN)
ALIMB = ANGLE OF OBSERVED OBJECT ABOVE (+) OR BELOW (-) LIMB
IN DEGREES (OUT)
AFRAC = NADIR ANGLE OF OBSERVED OBJECT AS A FRACTION OF
APPARENT RADIUS OF LIMB (OUT)
AFRAC<1.D0 MEANS BELOW THE LIMB
AFRAC=1.D0 MEANS ON THE LIMB
AFRAC>1.D0 MEANS ABOVE THE LIMB
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Nodes of different colours represent the following:
Solid arrows point from a procedure to one which it calls. Dashed
arrows point from an interface to procedures which implement that interface.
This could include the module procedures in a generic interface or the
implementation in a submodule of an interface in a parent module.