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StcsCoords - Return the Coordinates component when reading an STC-S document?

Description:
This is a boolean attribute which controls what is returned by the astRead function when it is used to read from an StcsChan. If StcsCoords is set non-zero, then a PointList representing the STC Coordinates will be returned by astRead. If StcsCoords is set to zero (the default), then the STC Coordinates will not be returned.
Type:
Integer (boolean).
Class Applicability:
StcsChan
All StcsChans have this attribute.
Notes:
  • Other attributes such as StcsArea and StcsProps can be used to specify other Objects to be returned by astRead. If more than one of these attributes is set non-zero, then the actual Object returned by astRead will be a KeyMap, containing the requested Objects. In this case, the PointList representing the STC Coordinates will be stored in the returned KeyMap using the key "COORDS". If StcsCoords is the only attribute to be set non-zero, then the Object returned by astRead will be the Coordinates PointList itself.

  • The Coordinates component is specified by the additional axis values embedded within the body of each STC-S sub-phrase that represents an extended area. Sub-phrases that represent a single value ( that is, have identifiers "Time", "Position", "Spectral" or "Redshift" ) are not considered to be be part of the STC Coordinates component.

  • If the STC-S documents does not contain a Coordinates component, then a NULL object pointer will be returned by astRead if the Coordinates component is the only object being returned. If other objects are also being returned (see attributes StcsProps and StcsArea), then the returned KeyMap will contain a "COORDS" key only if the Coordinates component is read succesfully.

  • The TimeFrame used to represent a time STC-S sub-phrase will have its TimeOrigin attribute set to the sub-phrase start time. If no start time is specified by the sub-phrase, then the stop time will be used instead. If no stop time is specified by the sub-phrase, then the single time value specified in the sub-phrase will be used instead. Subsequently clearing the TimeOrigin attribute (or setting its value to zero) will cause the TimeFrame to reprsent absolute times.

  • The Epoch attribute for the returned Region is set in the same way as the TimeOrigin attribute (see above).


next up previous 264
Next: StcsLength - Controls output line length
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council