[SAC-HELP] BBFK alphanumeric output from SAC

[George Helffrich]

Dear All -

	This is one of the darker areas of SAC (in the sense of 
documentation).  The reference cited in the code for the method is 
this:

Nawab, SH, FU Dowla, and RT Lacoss, Direction determination of wideband 
signals, IEEE Trans. Acous. Speech Sig. Proc., 33: (5), 1114-1122, 
1985.

	The WAVENUMBER parameter is a value in reciprocal kilometers, and is 
the maximum value that defines the extent of the X-Y grid of returned 
values.

	Assuming familiarity with reading SAC XYZ files, the value at every 
spatial point should be the F-K value, transformed by the method 
chosen:  MLM, Music or PDS.  MLM and Music will transform the F-K value 
to its reciprocal on output.  PDS does no transformation.

On 13 May 2009, at 21:04, Bob Myhill wrote:

> Dear all,
>
>  I've been trying for some time to plot bbfk data retrieved from SAC 
> (the 09/04/2008 version) in .a format, but do not understand the 
> structure of the data output.
>
>  The SAC manual informs me that the data is output in 'square mode', 
> but I don't know how this relates to the azimuth and wavenumber, and 
> how consecutive data points are chosen. I've tried both a simple 
> azimuthal and wavenumber progression (rotating around the z-axis or 
> radiating from it) but neither of these seem to recreate SACs own 
> output.
>
>  Could you give me some advice on how to read this data?
>
>  Many thanks,
>  Bob
>
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                                     George Helffrich
                                     george at geology.bristol.ac.uk