subroutine IRPL_GREATXSMALL
Purpose intersections between a great circle and a small circle
File irpl_greatxsmall.shl
Class IRAS, Math
Author 850712 Uwe Peppel
Use subroutine IRPL_GREATXSMALL(
polegc, I doubleprecision(3)
theta, I real
pint, O real(3,2)
nrint ) O integer
polegc coordinates of one pole of the great circle
theta polar angle of the small circle (in rad)
pint intersection points
nrint number of intersection points found
Description The input parameters have to be given in a rectangular
coordinate system with the z-axis pointing to the
center of the small circle. The great circle has to
be specified by the coordinates of one of its
poles, the small circle by its polar angle.
If intersection points are found, they are given by the
array PINT. nrint can be 0, 1, or 2. nrint =1 means that
the two circles have one common point. For the trivial case
of THETA = 90 and POLEGC = (0,0,1) where the two circles
are identical, nrint is given the value -1.
Update 900911 DK, all real variables to doubleprecision