astOffsetastOffset
-
Calculate an offset along a geodesic curve
Description:
This function finds the FrameFrame coordinate values of a point which
is offset a specified distance along the geodesic curve between
two other points.
For example, in a basic Frame, this offset will be along the
straight line joining two points. For a more specialised Frame
describing a sky coordinate system, however, it would be along
the great circle passing through two sky positions.
An array of double, with one element for each Frame axis
(NaxesNaxes attribute). This should contain the coordinates of the
point marking the start of the geodesic curve.
point2
An array of double, with one element for each Frame axis
This should contain the coordinates of the point marking the
end of the geodesic curve.
offset
The required offset from the first point along the geodesic
curve. If this is positive, it will be towards the second
point. If it is negative, it will be in the opposite
direction. This offset need not imply a position lying
between the two points given, as the curve will be
extrapolated if necessary.
point3
An array of double, with one element for each Frame axis
in which the coordinates of the required point will be returned.
Notes:
The geodesic curve used by this function is the path of
shortest distance between two points, as defined by the
astDistanceastDistance function.
This function will return "bad" coordinate values (AST__BAD)
if any of the input coordinates has this value.
"Bad" coordinate values will also be returned if the two
points supplied are coincident (or otherwise fail to uniquely
specify a geodesic curve) but the requested offset is non-zero.