- ←Prev
- AST
A Library for Handling
World Coordinate Systems
in Astronomy - Next→
- TOC ↑
Description:
This
routine returns the geometric parameters describing the supplied ellipse.
Invocation
CALL
AST_ELLIPSEPARS( THIS, CENTRE, A, B, ANGLE, P1, P2, STATUS )
Arguments
THIS =
INTEGER (Given)
CENTRE( 2 ) = DOUBLE PRECISION (Returned)
The
coordinates of the
Ellipse centre are returned in this arrays.
A = DOUBLE PRECISION
(Returned)
Returned holding the half-length of the first axis of the ellipse.
B = DOUBLE
PRECISION (Returned)
Returned holding the half-length of the second axis of the ellipse.
ANGLE = DOUBLE PRECISION (Returned)
If the coordinate system in which the Ellipse
is defined has axes (X,Y), then ANGLE is returned holding the angle from the positive
direction of the Y axis to the first axis of the ellipse, in radians. Positive rotation is in the same
sense as rotation from the positive direction of Y to the positive direction of X.
P1( 2 ) =
DOUBLE PRECISION (Returned)
An array in which to return the coordinates at one of
the two ends of the first axis of the ellipse.
P2( 2 ) = DOUBLE PRECISION (Returned)
An array in which to return the coordinates at one of the two ends of the second axis of
the ellipse.
STATUS = INTEGER (Given and Returned)
The global status.
Notes:
-
If the coordinate system represented by the Ellipse has been changed since it was first created, the
returned parameters refer to the new (changed) coordinate system, rather than the original coordinate
system. Note however that if the transformation from original to new coordinate system is
non-linear, the shape represented by the supplied Ellipse object may not be an accurate
ellipse.
-
Values of AST__BAD are returned for the parameters without error if the ellipse is degenerate or
undefined.
Copyright (C) 2021 East Asian Observatory
- ←Prev
- AST
A Library for Handling
World Coordinate
Systems
in Astronomy - Next→
- TOC ↑