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Berry, D. S. 2003, in ASP Conf. Ser., Vol. 314 Astronomical Data Analysis Software and Systems XIII, eds. F. Ochsenbein, M. Allen, & D. Egret (San Francisco: ASP), 412

Developments in the Starlink AST Library - an Intelligent WCS Management System

D.S. Berry
The Starlink Project, Rutherford Appleton Laboratory, Didcot, Oxfordshire, United Kingdom. OX11 0QX. Email: dsb@ast.man.ac.uk

Abstract:

Recent developments in the AST library for managing WCS information are described. These include support for spectral coordinate systems, and compliance with FITS WCS papers I, II and III.

1. The Starlink AST Library

2. What's New in AST

2.1 V2.0 - Highlights Only

2.2 V3.0 - Highlights Only

3. Coming Soon


Table 1: Support within AST V3.0 for FITS-WCS features.
Feature Status

Axis distortions (as described in paper IV)

Ignored (except for the SIRTF-specific ``-SIP'' code which is interpreted correctly when reading a FITS header, but is never written out to a new FITS header).

Alternate axis descriptions

Supported

User-defined fiducial points

Supported

Choice of PCi_ja or CDi_ja matrix

Supported

Deprecated WCS conventions (e.g. keyword CROTAi, EPOCH, PCiiijjj, the NCP projection, etc.)

Supported

Alternate keyword formats for inclusion in tables

Unsupported

Units in comment strings

Unsupported

Uncertainties in the coordinates

Unsupported

``WCSDEP'' convention

Unsupported

Use of longitude projection parameters to store LONPOLE and LATPOLE

Supported

Common, non-standard features

Support for reading (but not writing) various common, non-standard feature such as ``TNX'' and ``ZPX'' projections is included. More can easily be added as requested.



Table 2: Support within AST V3.0 for FITS-WCS keywords.
Keyword Description Status

WCSAXESa

WCS dimensionality Supported

CRVALia

Value at reference point Supported

CRPIXja

Pixel of reference point Supported

CDELTia

Increment at reference point Supported

CROTAi

Rotation at reference point Supported (only written when producing a ``FITS-AIPS'' header)

CTYPEia

Coordinate/algorithm/distortion type Supported (all coordinate systems [including helio-ecliptic] and algorithm codes listed in papers I, II and III, with the exception of the ``STOKES'' and ``COMPLEX'' values defined in paper I, the ``CUBEFACE'' value defined in paper II, and the ``-TAB'' algorithm defined in paper III)

CUNITia

Units of coordinate values Supported (including automatic unit conversion if the units strings conform to paper I conventions)

PCi_ja

Transformation matrix Supported

CDi_ja

Transformation matrix Supported

PVi_ma

Algorithm numerical parameter Supported

PSi_ma

Algorithm textual parameter Unsupported

WCSNAMEa

Coordinate version name Supported

CRDERia

Random error Unsupported

CSYERia

Systematic error Unsupported

LONPOLEa

Coordinate rotation (celestial axes) Supported

LATPOLEa

Coordinate rotation (celestial axes) Supported

RADESYSa

Frame of reference (celestial axes) Supported (all systems, except ecliptic coordinates are currently assumed to be FK5)

EQUINOXa

Coordinate epoch (celestial axes) Supported

EPOCH

Coordinate epoch (celestial axes) Supported (only written when producing a ``FITS-AIPS'' header)

MJD-OBS

Time of observation Supported

SPECSYSa

Spectral reference frame Supported (all systems, except CMBDIPOL)

SSYSOBSa

Spectral reference frame fixed during observation Unsupported

OBSGEO-X/Y/Z

Observation position Supported

MJD-AVG

Average date of observation Supported

VSOURCEa

Physical velocity of source for SPECSYS=SOURCE cases Supported

ZSOURCEa

Optical velocity of source for SPECSYS=SOURCE cases Supported

VELOSYSa

Velocity w.r.t. standard of rest Unsupported

RESTFRQa

Line rest frequency Supported

RESTWAVa

Line rest wavelength in vacuum Supported

CNAMEia

Descriptive axis label Supported



© Copyright 2004 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
Next: Interoperating GILDAS and MIRIAD
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