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...Display Coordinates as they are Transformed

In addition to formatting coordinates as part of a program's output, you may also want to examine coordinate values while debugging your program. To save time, you can ``eavesdrop'' on the coordinate values being processed every time they are transformed. For example, when using the FrameSet pointer ``wcsinfo'' obtained in [*] to transform coordinates ([*]), you could inspect the coordinate values as follows:

astSet( wcsinfo, "Report=1" );
astTran2( wcsinfo, N, xpixel, ypixel, 1, xworld, yworld );

By setting the FrameSet's Report attribute to 1, coordinate transformations are automatically displayed on the program's standard output stream, appropriately formatted, for example:

(42.1087, 20.2717) --> (2:06:03.0, 34:22:39)
(43.0197, 21.1705) --> (2:08:20.6, 35:31:24)
(43.9295, 22.0716) --> (2:10:38.1, 36:40:09)
(44.8382, 22.9753) --> (2:12:55.6, 37:48:55)
(45.7459, 23.8814) --> (2:15:13.1, 38:57:40)
(46.6528, 24.7901) --> (2:17:30.6, 40:06:25)
(47.5589, 25.7013) --> (2:19:48.1, 41:15:11)
(48.4644, 26.6149) --> (2:22:05.6, 42:23:56)
(49.3695, 27.5311) --> (2:24:23.1, 43:32:41)
(50.2742, 28.4499) --> (2:26:40.6, 44:41:27)

For a complete description of the Report attribute, see its entry in [*]. For further details of how to set and enquire attribute values, see [*] and [*].


next up previous 264
Next: ...Read Coordinates Entered by a User
Up: How To...
Previous: ...Format Coordinates for Display

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
25th February 2013
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2014 Science \& Technology Facilities Council