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AST_RESOLVE
-
Resolve a vector into two orthogonal components
- Description:
- This routine resolves a vector into two perpendicular components.
The vector from point 1 to point 2 is used as the basis vector.
The vector from point 1 to point 3 is resolved into components
parallel and perpendicular to this basis vector. The lengths of the
two components are returned, together with the position of closest
aproach of the basis vector to point 3.
- Invocation:
- CALL AST_RESOLVE( THIS, POINT1, POINT2, POINT3, POINT4, D1, D2,
STATUS )
- Arguments:
-
THIS = INTEGER (Given)
-
Pointer to the Frame.
-
POINT1(
) = DOUBLE PRECISION (Given)
-
An array with one element for each Frame axis
(Naxes attribute). This marks the start of the basis vector,
and of the vector to be resolved.
-
POINT2(
) = DOUBLE PRECISION (Given)
-
An array with one element for each Frame axis
(Naxes attribute). This marks the end of the basis vector.
-
POINT3(
) = DOUBLE PRECISION (Given)
-
An array with one element for each Frame axis
(Naxes attribute). This marks the end of the vector to be
resolved.
-
POINT4(
) = DOUBLE PRECISION (Returned)
-
An array with one element for each Frame axis
in which the coordinates of the point of closest approach of the
basis vector to point 3 will be returned.
-
D1 = DOUBLE PRECISION (Returned)
-
The distance from
point 1 to point 4 (that is, the length of the component parallel
to the basis vector). Positive values are in the same sense as
movement from point 1 to point 2.
-
D2 = DOUBLE PRECISION (Returned)
-
The distance from
point 4 to point 3 (that is, the length of the component
perpendicular to the basis vector). The value is always positive.
-
STATUS = INTEGER (Given and Returned)
-
The global status.
- Notes:
- Each vector used in this routine is the path of
shortest distance between two points, as defined by the
AST_DISTANCE function.
- This function will return "bad" coordinate values (AST__BAD)
if any of the input coordinates has this value, or if the required
output values are undefined.
Next: AST_RETAINFITS - Indicate that the current card in a FitsChan should be retained
Up: AST Routine Descriptions
Previous: AST_RESAMPLEX - Resample a region of a data grid
AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council