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Description:
This function 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.
Synopsis
void astResolve( AstFrame
$\ast $this,
const double point1[], const double point2[], const double point3[], double point4[],
double $\ast $d1,
double $\ast $d2
);
Parameters:
this
point1
An array of double, 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
An array of
double, with one element for each Frame axis (Naxes attribute). This marks
the end of the basis vector.
point3
An array of double, with one element
for each Frame axis (Naxes attribute). This marks the end of the vector to be
resolved.
point4
An array of double, 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
The address of a location at which to return
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
The address of a location at which to return
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.
Notes:

Each vector used in this function is the path of shortest distance between two points,
as defined by the astDistance 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.
Copyright (C) 2021 East Asian Observatory
 ←Prev
 AST
A Library for Handling
World
Coordinate Systems
in Astronomy  Next→
 TOC ↑