天文
用FITS - 'Flexible Image
Transport System' - 格式簡介
什麼是FITS?
- 天文學界的標準資料格式
- 為'Flexible Image Transport System'的縮寫
- 由NASA及國際天文學會所大力支持
- 比其他影像格式更加強大(諸如JPEG或GIF), 適用於科學研究環境
- 用於傳輸, 分析, 及儲存科學用資料
- 多維空間陣列: 1D spectra, 2D images, 3D+ data cubes
- 表格包含了欄及列的資訊
- 表頭關鍵字提供了關於資料方面的描述
FITS文件
FITS簡介
FITS是一個天文學家經常使用的電腦檔案資料格式, 用以傳輸, 分析及儲存科學資料.
FITS的歷史
The following paragraphs are reproduced from the 'Introduction' to the FITS Standard
document.
The Flexible Image Transport System (FITS) evolved out of the
recognition that a standard format was needed for transferring
astronomical data from one installation to another. The original form,
or Basic FITS, was designed for the transfer of images and consisted of
a binary array, usually multidimensional, preceded by an ASCII text
header with information describing the organization and contents of the
array. The FITS concept was later expanded to accommodate more complex
data formats. A new format for image transfer, random groups, was
defined in which the data would consist of a series of arrays, with
each array accompanied by a set of associated parameters.
These formats were formally endorsed by the International
Astronomical Union (IAU) in 1982. Provisions for data structures other
than simple arrays or groups were made later. These structures appear
in extensions, each consisting of an ASCII header followed by the data
whose organization it describes. A set of general rules governing such
extensions and a particular extension, ASCII table, were endorsed by
the IAU General Assembly in 1988. At the same General Assembly, an IAU FITS Working Group (IAUFWG) was
formed under IAU Commission 5 (Astronomical Data) with the mandate to
maintain the existing FITS standards and to review, approve, and
maintain future extensions to FITS, recommended practices for FITS,
implementations, and the thesaurus of approved FITS keywords. In 1989,
the IAUFWG approved a formal agreement for the representation of
floating point numbers. In 1994, the IAUFWG endorsed two additional
extensions, the image extension and the binary table extension.
FITS was originally designed and defined for 9-track half-inch
magnetic tape. However, as improvements in technology have brought
forward other data storage and data distribution media, it has
generally been agreed that the FITS format is to be understood as a
logical format and not defined in terms of the physical characteristics
of any particular data storage medium. In 1994, the IAUFWG adopted a
set of rules governing the relation between the FITS logical record
size and the physical block size for sequential media and bitstream
devices. The IAUFWG also approved in 1997 an agreement defining a new
format for encoding the date and time in the DATE, DATE-OBS, and other
related DATExxxx keywords to correct the ambiguity in the original DATE
keyword format beginning in the year 2000.
In December 2002, after more than a decade of complex negotiations,
the IAUFWG approved 2 papers that deal with the issue of representing
World Coordinate Systems (WCS) in FITS. Two more papers in this WCS
series are currently under development.
Brief highlights of the history of FITS:
- 1979年: 開始使用並進行FITS資料交換
- 1980年: Random groups convention developed
- 1981年: Published original (single HDU) definition paper
- 1981年: Published random groups definition paper
- 1982年: FITS格式正式由IAU所背書
- 1988年: Defined rules for multiple HDUs in a FITS file
- 1988年: FITS工作群由IAU (IAUFWG)建立
- 1988年: FITS definition extended to include ASCII TABLE extensions
- 1990年: FITS definition extended to include IEEE floating-point
data
- 1994年: FITS definition extended to multiple image arrays in IMAGE
extensions
- 1995年: FITS definition extended to binary tables in BINTABLE
extensions
- 1997年: 採用Y2K相容日期格式
- 2001年: Reiterated existing standard in one paper (NOST文件)
- 2002年: Approved conventions for generalized world coordinates and
celestial coordintates.
How FITS Evolves
The IAU-FWG was given authority over
FITS matters by the 1988 IAU General
Assembly. When the developer of a data set finds that it does not fit
well into the primary HDU or a standard extension format, a new design
may be developed. No change can be made that would cause existing FITS
files to be out of conformance -- the "once FITS, always FITS" rule.
Because software to read FITS files uses the type name of an extension
to determine whether or not the software can read the extension,
extension type names must be unique. The IAUFWG maintains a list of extension type names that have been
registered; the list is at the FITS Support Office. A unique name
for any new extension type, even a developmental extension or one that
will be used only locally, must be registered with the IAU-FWG. After
astronomical community discussion, a formal proposal is distributed.
This proposal is discussed by the community and may be further
modified. Tests are run using the new format to confirm that it can be
practically used for data transport. If the astronomical community
reaches a consensus that the proposal should be adopted as standard
FITS, and if successful data transfer using the proposed extension can
be demonstrated, it is submitted for ratification to the regional
committees -- the European FITS Committee, the Japanese FITS Committee,
and the American Astronomical Society Working Group on Astronomical
Software (WGAS)
FITS Committee. Following approval by the regional committees, it
is submitted to the IAU-FWG Approval by the IAU-FWG establishes it as a
standard extension.
In addition to the formal rules, a number of conventions are widely
observed. Some conventions are used throughout the community others
only within a particular discipline such as high energy astrophysics or
single dish radio astronomy. Usually, the originator(s) of a convention
will circulate an initial proposal for comments among a small group in
the same discipline or installation. After this proposal has been
refined based upon these comments, it is put out for public comment,
usually by announcement to the sci.astro.fits
newsgroup of a URL from which it can be retrieved. Comments at this
time may lead to additional changes. If the affected community accepts
the convention, installations will start using it in their FITS files.
Since failure to use a convention is not a violation of the FITS rules,
FITS readers unaware of it must not terminate with an error or give
incorrect results when encountering it.
-
- FITS Format Primer - introduction
to the basic structure of a FITS file
- The FITS Standard - the definitive reference document that
defines the FITS format
- Version
2.1b - this is the latest version of the FITS Standard that
reflects the changes that were approved by the FITS Working Group in December and April
2005.
- NOST
FITS Standard, version 2.0 (also available in PDF,
or Postscript
formats).
This 96 page document was developed by the NOST technical panel in
March 1999.
(The original LaTeX format text
file and 4 required ancillary files style
file, index
file, ieee1.eps,
and ieee2.eps
are also available).
- The published
version of the NOST document is available online by subscription
from the A&A journal in HTML
format. An unrestricted
PDF version (containing only the main body of the paper, minus the
appendixes) has been made available here by permission of the
publisher. This published version of the FITS Standard was endorsed by
the IAU FITS Working Group in October
2000 and is identical to the original NOST document except for the
addition of 2 introductory sections on the history of FITS and on the
process that lead to the creation of the NOST document. There were also
2 minor clarifications on a) the interpretation of the word
"deprecated" and b) the usage of the TDIMn keyword with variable length
array columns.
- World Coordinate System (WCS) -
documents and software dealing with world coordinate system
conventions. The first 3 WCS papers have been approved by the IAU-FWG and are now officially
recognized as part of the FITS Standard.
- FITS MIME types (RFC 4047) - The Internet Engineering Task Force
issued this Internet standards document that defines and registers the
"image/fits" and "application/fits" MIME types in April 2005 after a long review process.
The MIME types are typically used to describe the type of content (or
media type) of documents or data files that are passed between
applications over the Internet. The MIME type indicates to the
receiveing application (e.g., a web browser) how to handle the
information.
- FITS User's
Guide - an out of date (April 1997) introduction to the history and
usage of FITS. This document does not reflect the changes that were
introduced in version 2.0 of the FITS Standard that was approved in the
year 2000, nor does it address the FITS conventions that are defined in
the series of World Coordinate System (WCS)
papers that have been approved by the FITS
Working Group. The User's guide is also available in PDF
and postscript
formats, as well as the LaTeX
source text file and style
file.
- FITS extensions - list of extension
names registered with the IAU FITS
Working Group
- FITS Birthday Announcement -
Historical note from Don Wells on the events leading up to the 'birth'
of the FITS format in 1979.
- Historical Perspectives on FITS
(PDF) by Eric Greisen, one of the original developers of FITS. This
paper was published in Information Handling in Astronomy -
Historical Vistas, edited by Andre Heck (Kluwer, Astrophysics and
Space Science Library, 285 (2002). It is also available in postscript format.
- FITS comparison - a draft
document written in 1992 by Barry Schlesinger (then the FITS support
person at GSFC-NOST) as part of a comparison of various data formats
that was produced by NOST.
- Formats Evolution
Process established several discussion
forums for contrasting and comparing different data formats,
including FITS, HDF, and CDF. Several researchers and archive sites
present their experiences in using the FITS format.
FITS世界坐標系統(WCS)
WCS文件
An elaborate set of FITS conventions has been defined to specify the
physical, or world, coordinates to be attached to each pixel of an
N-dimensional image. By world coordinates, one means coordinates that
serve to locate a measurement in some multi-dimensional parameter
space. A common example is to specify the Right Ascension and
Declination on the sky associated with a given the pixel location in a
celestial image.
- The WCS conventions are currently described in a set of 4 papers.
The first 3 papers have been approved by the IAU-FWG and are now
officially recognized as part of the FITS Standard.
- Representations
of World Coordinates in FITS, Greisen, E. W., and Calabretta, M.
R., Astronomy & Astrophysics, 395, 1061-1075,
2002. (PDF,
HTML).
(These links to the publisher's web site are currently available by
subscription only). Reprints are available from the author's web site in PDF
format.
- Representations
of celestial coordinates in FITS Calabretta, M. R., and Greisen, E.
W., Astronomy & Astrophysics, 395, 1077-1122,
2002. (PDF,
HTML).
(These links to the publisher's web site are currently available by
subscription only). Reprints are available from the author's web site in PDF
format.
An unofficial errata for Papers I and II is available in postscript or pdf format.
- "Representations of spectral coordinates in FITS", Greisen,
E. W., Calabretta, M. R., Valdes, F. G., and Allen, S. L., Astronomy
& Astrophysics, (in press). The latest draft of this paper
is available from the author's web site.
- "Representaions of distortions in FITS world coordinate
systems" by Calabretta, et al. The latest draft of this paper are
available from the author's web site. A related
proposal by Steve Allen and Doug Mink for concatenating WCS keywords
eventually may be incorporated into the final version of 4th WCS paper.
Other WCS papers:
- "Mapping on the HEALPix grid" by Calabretta & Roukema
introduces the HPX spherical projection type as an addendem to the 2nd
WCS paper listed above. This paper is available in postscript or pdf format. The HEALPix projection, as
defined in section 6 of this paper, was approved as part of the
official FITS WCS standard by the IAU-FWG on 26 April 2006.
- "Coordinate
Systems for Solar Image Data" by Bill Thompson proposes a set of
formal systems for descibing the coordinates of solar image data,
including heliographic and heiocentric coordinates.
WCS軟體
以下軟體程式庫都可以簡化在世界坐標系轉換上,有關於投射及坐標轉換的實作.
- WCSLIB
- Mark Calabretta's subroutines for spherical projections and
coordinate transformations.
- WCSTools
- Doug Mink's subroutines and utilities to convert between sky and
image coordinates.
- AST library -
Astrometry and World Coordinate System handling routines from the U.K.
Starlink Project. Includes graphical display routines for plotting axes
and labelled coordinate grids.
有關於FITS的資訊
ADASS Conference Papers
Related
to FITS
This list only contains the papers that are primarily focused on FITS
issues. Many other papers that are more indirectly related to the FITS
format or data processing issues can be found in the ADASS
database.
ADASS
I - 1991, ASP Conference Series, Vol. 25.
ADASS
II - 1992, ASP Conference Series, Vol. 52.
- The
ROSAT Implementation of a Proposed Multi-Mission X-ray Data Format,
Corcoran, M. F., et al.
- FITS
Data Conversion Efforts at the Compton Observatory Science Support
Center, Jennings, D. G., et al.
- FTOOLS---A
FITS Utility Package for Multiple Environments, Pence, W. et al.
- The
IRAF/NOAO Spectral World Coordinate Systems, Valdes, F.
ADASS
III - 1993, ASP Conference Series, Vol. 61.
ADASS IV -
1994, ASP Conference Series, Vol. 77.
- Proposed
FITS Keywords and Column Headers for ALEXIS Mission Data Files, J.
Bloch and J. Theiler
- The
OGIP FITS Working Group M. F. Corcoran, et al.
- A
Generic Data Exchange Scheme Between FITS Format and C Structures,
W. Peng and T. Nicinski
- Reformatting
the Ginga Database to FITS and the Creation of a Data Products Archive,
R. H. D. Corbet, et al.
- Representations
of Celestial Coordinates in FITS, E. W. Greisen, M. Calabretta
- A
Proposed Convention for Writing FITS Data Tapes: DRAFT 0,
ROSAT/ASCA/XTE Development Team
- FITSIO
Subroutine Library Update, W. D. Pence
- FITS
Checksum Verification in the NOAO Archive, R. Seaman
- FTOOLS:
A FITS Data Processing and Analysis Software Package, J. K.
Blackburn
ADASS
V - 1995, ASP Conference Series, Vol. 101.
ADASS VI -
1996, ASP Conference Series, Vol. 125.
- Practical
Applications of a Relational Database of FITS Keywords, De Clarke
and S. L. Allen
- Multiple
World Coordinate Systems for DEIMOS Mosaic Images, S. L. Allen, De
Clarke
- WCSTools:
Image World Coordinate System Utilities, D. J. Mink
- The
SAOtng Programming Interface, E. Mandel
- Speculations
on the Future of FITS, Donald C. Wells
- FV:
A New FITS File Visualization Tool, W. Pence, J. Xu, L. Brown
- FITS++:
An Object-Oriented Set of C++ Classes to Support FITS, A. Farris
- The
FITS List Calculator and Bulk Data Processor, E. B. Stobie and D.
M. Lytle
- FITS
BoF Session, P Teuben, D Wells
ADASS
VII - 1997, ASP Conference Series, Vol. 145.
ADASS VIII -
1998, ASP Conference Series, Vol. 172.
ADASS IX -
1999, ASP Conference Series, Vol. 216.
ADASS X -
2000, ASP Conference Series, Vol. 238.
ADASS XI - 2001, ASP Conference Series, Vol. 281. (not currently
available) ADASS
XII - 2002, ASP Conference Series, Vol. 295.
ADASS XIII -
2003, ASP Conference Series, Vol. 314.
- Chandra
FITS Dictionary, S. L. Winkelman, A. H. Rots, K. Michaud, and S. E.
Blecksmith
- Developments
in the Starlink AST Library - an Intelligent WCS Management System,
D. S. Berry
- Making
FITS available on Dot Net and its applications, V. Haridas, T.
Budavári, W. O'Mullane, A. S. Szalay, A. Thakar, A. Conti, A.
Volpicelli, and B. Pence
- Representations
of distortions in FITS world coordinate systems, M. R. Calabretta,
F. Valdes, E. W. Greisen, and S. L. Allen
- Demo of
numarray, PyFITS, and related software, J.-C. Hsu and P. E. Hodge
Published FITS Definition Papers
- FITS:
A Flexible Image Transport System, Wells, D. C., Greisen, E. W.,
and Harten, R. H., Astronomy & Astrophysics Supplement Series,
44, 363-370, 1981. (HTML,
PDF)
- An
Extension of FITS for Groups of Small Arrays of Data, Greisen, E.
W. and Harten, R. H., Astronomy & Astrophysics Supplement
Series, 44, 371-374, 1981. (NOTE: The random groups
format described in this paper has been used almost exclusively to
transport radio interferometry and has now largely been replaced by
binary tables. Writing data other than radio interferometry data using
this format is not recommended.) (HTML,
PDF)
- Generalized
Extensions and Blocking Factors for FITS, Grosbøl, P.,
Harten, R. H., Greisen, E. W., and Wells, D. C., Astronomy &
Astrophysics Supplement Series, 73, 359-364, 1988. (HTML,
PDF)
- The
FITS Tables Extension, Harten, R. H., Grosbøl. P., Greisen,
E. W., and Wells, D. C., Astronomy & Astrophysics Supplement
Series, 73, 365-372, 1988. (HTML,
PDF)
- The
FITS Image Extension, Ponz, J. D., Thompson, R. W., and Munoz, J.
R., Astronomy & Astrophysics Supplement Series, 105,
53-55, 1994. (HTML,
PDF)
- Binary
Table Extension to FITS, Cotton, W. D., Tody, D. B., and Pence, W.
D., Astronomy & Astrophysics Supplement Series, 113,
159-166, 1995. (HTML,
PDF)
- Definition
of the Flexible Image Transport System (FITS), Hanisch, R. J.,
Farris, A., Greisen, E. W., Pence, W. D., Schlesinger, B. M., Teuben,
P. J., Thompson, R. W., and Warnock, A., Astronomy &
Astrophysics, 376, 359-380, 2001. (HTML,
PDF).
These links to the publisher's web site are currently available by
subscription only. The PDF version includes only the main body of the
paper and not the appendixes. An unrestricted
PDF version has been made available here by permission of the
publisher. The original NOST
version of the Standard is available in HTML, PDF,
and Postscript
formats.
- Representations
of World Coordinates in FITS, Greisen, E. W., and Calabretta, M.
R., Astronomy & Astrophysics, 395, 1061-1075, 2002. (PDF,
HTML).
(These links to the publisher's web site are currently available by
subscription only). Reprints are also available from the author's web
site in PDF
format.
- Representations
of Celestial Coordinates in FITS, Calabretta, M. R., and Greisen,
E. W., Astronomy & Astrophysics, 395, 1077-1122,
2002. (PDF,
HTML).
(These links to the publisher's web site are currently available by
subscription only). Reprints are also available from the author's web
site in PDF
format.
2006/6/4日更新, 中微子國際股份有限公司
