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astAxDistance - Find the distance between two axis values

Description:
This function returns a signed value representing the axis increment from axis value v1 to axis value v2. For a simple Frame, this is a trivial operation returning the difference between the two axis values. But for other derived classes of Frame (such as a SkyFrame) this is not the case.

Synopsis:
double astAxDistance( AstFrame *this, int axis, double v1, double v2 )

Parameters:
this
Pointer to the Frame.
v1
The first axis value.
v2
The second axis value.

Returned Value:
astAxDistance
The distance between the two axis values.

Notes:
  • This function will return a "bad" result value (AST__BAD) if any of the input vaues has this value.
  • A "bad" value will also be returned if this function is invoked with the AST error status set, or if it should fail for any reason.



next up previous
Next: astAxOffset - Add an increment onto a supplied axis value
Up: AST Function Descriptions
Previous: astAxAngle - Returns the angle from an axis, to a line through two points

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
30th April 2003
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2003 Central Laboratory of the Research Councils