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Summary: Review Request: ast - A Library for Handling World Coordinate Systems in
Summary: Review Request: ast - A Library for Handling World
Coordinate Systems in Astronomy
Component: Package Review
CC: notting(a)redhat.com, fedora-package-review(a)redhat.com
Estimated Hours: 0.0
Story Points: ---
Spec URL: http://www.cora.nwra.com/~orion/fedora/ast.spec
SRPM URL: http://www.cora.nwra.com/~orion/fedora/
Description:The AST library provides a comprehensive range of facilities for
world coordinate systems to astronomical data, for retrieving and interpreting
that information and for generating graphical output based on it. It's main
selling points are:
* Ease of use.
* Facilities for generating plots of generalized non-linear, potentially
discontinuous 2-D or 3-D coordinate systems, with detailed control of the
appearance of the plot.
* Facilities for converting transparently between different coordinate
systems, including a wide range of celestial, spectral and time coordinate
* Facilities for searching a general collection of connected coordinate
systems for a coordinate system with any given set of characteristics.
* Allows code for handling WCS information to be written in a general way
without regard to the specific nature of the coordinate systems being
handled (i.e. whether they represent sky positions, spectral positions,
focal plane positions, pixel positions, etc).
* Flexible system for saving and retrieving WCS information, including (but
not limited to) a range of different popular FITS descriptions.
* Written in C but has interfaces for C, Fortran, Java (via JNI), Perl, and
* Extensive documentation.
AST is different to other popular FITS-based WCS packages in that it takes a
very high level, generalized "object oriented" view of the problems of
describing, using and storing WCS information. For this reason, it is very
easy to use - it wraps up all the complications of dealing with the specifics
of different classes of coordinate systems (celestial, spectral, pixel, etc).
Another reason it is easy to use is that it hides completely the sometimes
elaborate details of FITS WCS handling, and uses a completely FITS-independent
and much cleaner interface more closely associated with the general nature of
world coordinate information. However, it is possible to go both ways between
AST and FITS (albeit the AST representations are much richer than the FITS and
so some information may be lost in going from AST to FITS).
All coordinate systems are described by "Frame" objects which encapsulate
information about the nature of the coordinate system - axis labels, units,
how to convert axis values to and from text strings, how to "measure distance"
within the Frame (the Frame metric), etc, etc. There are then subclasses of
Frame which "know" about more specific coordinate systems - at the moment the
three main subclasses are SkyFrame (which describes celestial positions on the
sky), SpecFrame (which describes positions within a spectrum) and TimeFrame
(which describes moments in time). All these classes can describe positions
within their respective domains using all the common coordinate systems
(various equatorial, ecliptic, galactic, etc for sky positions, wavelength
frequency, various velocities, etc, for spectral, different timescales, etc,
for time). They also know how to transform axis values between these systems.
There is also a "compound Frame" class which allows any two Frames (of any
class) to be joined together (for instance, you could compound a SkyFrame and
a SpecFrame to describe a spectral cube). These various forms of Frame can be
connected together using "Mappings". A Mapping is a mathematical recipe for
transforming a position within one coordinate system into another. There are
subclasses of Mapping which implement a wide range of different transformation.
* all the celestial projections and spectral algorithms described in FITS-WCS
papers II & III (currently excluding the "-TAB" algorithm),
* classes which allows the caller to define their own transformations, either
by providing a routine written in C or Fortran, or by providing a general
algebraic FORTRAN-like expression supplied in a text string.
* classes for scaling, shifting, pin cushion distortion, spherical to
Cartesian transformation, axis permutations, look-up table transformations,
* a class which allows any two other Mappings to be combined together either
in series or in parallel, to form a "compound Mapping". This allows Mappings
of arbitrary complexity to be constructed using the other Mappings as
A "FrameSet" is a collection of Frames connected together by Mappings. A
FrameSet can be created from a FITS header (for instance) using a single call.
The FrameSet can then be used to transform positions between nominated
coordinate systems, to convert axis values to and from text strings using
formats automatically chosen to be appropriate to the class of Frame, to plot
coordinate grids (using any graphics system you like), etc. FrameSets can be
searched for Frames with particular characteristics.
There are a large number of rpmlint warnings like:
ast.i686: W: undefined-non-weak-symbol /usr/lib/libast.so.0.0.0 astAZPfwd
This is caused by a rather strange library configuration. However, this is
expected and is worked around by using the ast_link command.
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