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The following describes the most significant changes which occurred in
the AST library between versions V1.0 and V1.1 (not the most recent
version):
- A new ``How To...'' section (
) has been
added to this document. It contains simple recipies for performing
commonly-required operations using AST.
- A new AST_UNFORMAT function has been provided to read formatted
coordinate values for the axes of a Frame
(
). In essence, this function is the
inverse of AST_FORMAT. It may be used to decode user-supplied
formatted values representing coordinates, turning them into numerical
values for processing. Celestial coordinates may also be read using
this function (
) and free-format
input is supported.
- The Format attribute string used by a SkyFrame when formatting
celestial coordinate values now allows the degrees/hours field to be
omitted, so that celestial coordinates may be given in (e.g.)
arc-minutes and/or arc-seconds
(
). As a result, the degrees/hours
field is no longer included by default. A new ``t'' format specifier
has been introduced (see the Format attribute) to allow minutes and/or
seconds of time to be specified if required.
- A new routine AST_MAPBOX has been introduced. This allows you
to find the extent of a ``bounding box'' which just encloses another
box after it has been transformed by a Mapping. A typical use might be
to calculate the size which an image would have if it were transformed
by the Mapping.
- A new class of Object, the IntraMap, has been introduced
(
). This is a specialised form of Mapping which
encapsulates a privately-defined coordinate transformation routine
(e.g. written in Fortran) so that it may be used like any
other AST Mapping. This allows you to create Mappings that perform any
conceivable coordinate transformation.
- The internal integrity of a FrameSet is now automatically
preserved whenever changes are made to any attributes which affect the
current Frame (either by setting or clearing their values). This is
accomplished by appropriately re-mapping the current Frame to account
for any change to the coordinate system which it represents
(
).
- The internal structure of a FrameSet is now automatically tidied
to eliminate redundant nodes whenever any of its Frames is removed or
re-mapped. Automatic simplification of any compound Mappings which
result may also occur. The effect of this change is to prevent the
accumulation of unnecessary structure in FrameSets which are
repeatedly modified.
- Some improvements have been made to the algorithms for
simplifying compound Mappings, as used by AST_SIMPLIFY.
- The textual representation used for some Objects
(i.e. when they are written to a Channel) has changed
slightly, but remains compatible with earlier versions of AST.
- A problem has been fixed which could result when using AST_READ
to read FITS headers in which the CDELT value is zero. Previously,
this could produce a Mapping whose inverse transformation was not
defined and this could unnecessarily restrict the use to which it
could be put. The problem has been overcome by supplying a suitable
small CDELT value for FITS axes which have only a single pixel.
- A bug has been fixed which could occasionally cause a MatrixMap
to be used with the wrong Invert attribute value when it forms part of
a compound Mapping which is being simplified using AST_SIMPLIFY.
- A bug has been fixed which could cause the AST__BAD parameter
to have an incorrect value on some platforms.
- A problem has been fixed which could prevent tick marks being
drawn on a coordinate axis close to a singularity in the coordinate
system.
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Up: Changes and New Features
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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