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DssMap - Map points using a Digitised Sky Survey plate solution

Description:
The DssMap class implements a Mapping which transforms between 2-dimensional pixel coordinates and an equatorial sky coordinate system (right ascension and declination) using a Digitised Sky Survey (DSS) astrometric plate solution.

The input coordinates are pixel numbers along the first and second dimensions of an image, where the centre of the first pixel is located at (1,1) and the spacing between pixel centres is unity.

The output coordinates are right ascension and declination in radians. The celestial coordinate system used (FK4, FK5, etc.) is unspecified, and will usually be indicated by appropriate keywords in a FITS header.

Constructor Function:
The DssMap class does not have a constructor function. A DssMap is created only as a by-product of reading a FrameSet (using AST_READ) from a FitsChan which contains FITS header cards describing a DSS plate solution, and whose Encoding attribute is set to "DSS". The result of such a read, if successful, is a FrameSet whose base and current Frames are related by a DssMap.

Inheritance
The DssMap class inherits from the Mapping class.

Attributes
The DssMap class does not define any new attributes beyond those which are applicable to all Mappings.

Functions
The DssMap class does not define any new routines beyond those which are applicable to all Mappings.



next up previous
Next: FitsChan - I/O Channel using FITS header cards to represent Objects
Up: AST Class Descriptions
Previous: CmpMap - Compound Mapping

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
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