'Name:        sphere-angle.ave
'Function:    Calculate angle (ABC) made from three points (A,B,C) basing on a sphere.
'Author:      Maxim Dubinin
'             sim@gis-lab.info
'Created      16:42 31.05.2006
'Last Update: 16:42 31.05.2006
'Notes: This script is used in Argos-tools. For calculating another script called Great-circles is needed.

pntlist = SELF

'distance calculation using greate cirlces (separate script)
pnts = {pntlist.get(0), pntlist.get(1), pntlist.get(3),pntlist.get(4)}
'AB
c = av.run("MD.ARGOS.GreatCirclesDist", pnts).Get(1)

pnts = {pntlist.get(1), pntlist.get(2), pntlist.get(4),pntlist.get(5)}
'BC
a = av.run("MD.ARGOS.GreatCirclesDist", pnts).Get(1)

pnts = {pntlist.get(0), pntlist.get(2), pntlist.get(3),pntlist.get(5)}
'AC
b = av.run("MD.ARGOS.GreatCirclesDist", pnts).Get(1)

B = (((b.cos) - ((a.cos)*(c.cos)))/((a.sin)*(c.sin))).ACos.AsDegrees

return B