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PL2EL

       SUBROUTINE  PL2EL (XI,ETA,VISBLE)
 C$    (2-D Elliptical Coordinate Pen Movement)
 C$    Change the variables (XI,ETA) to the Cartesian  coordinates
 C$    (X,Y)  so  as  to  define  points  directly  in  elliptical
 C$    coordinates and graph  their projection on  the X-Y  plane,
 C$    where the Y axis is vertical and the X axis is positive  to
 C$    the right.  (XI,ETA) are both  assumed to be scaled to  the
 C$    unit  interval.   The   Cartesian  coordinates  (X,Y)   are
 C$    adjusted to the  unit interval and  passed to  MOVA2/LINA2.
 C$    Elliptical coordinate ranges are
 C$
 C$    0.0 .LE. U .LE. infinity
 C$    0.0 .LE. V .LE. 2*pi
 C$
 C$    See H. Margenau  and G.M. Murphy,  "Mathematics of  Physics
 C$    and Chemistry", 2nd  Ed., Van  Nostrand (1956),  Vol 1,  p.
 C$    182.  These are related to the Cartesian coordinates by
 C$
 C$    X = A COSH(U) COS(V)
 C$    Y = A SINH(U) SIN(V)
 C$
 C$    where the semi-major axis is "A".  The coordinate  surfaces
 C$    are
 C$    (1) elliptic cylinders (U = constant)
 C$    (2) hyperbolic cylinders (V = constant)
 C$
 C$    To obtain  coordinates  (XI,ETA),  expressed  on  the  unit
 C$    interval, (U,V) are transformed as follows:
 C$
 C$    XI = U/UMAX
 C$    ETA = V/TWOPI
 C$
 C$    To obtain  a reasonable  scaling,  the semi-major  axis  is
 C$    chosen to be  A = 1/COSH(UMAX)  = 0.5, from  which UMAX  is
 C$    found to be UMAX = ARCCOSH(2.0) = 1.3169578.
 C$    (09-APR-82)