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 SURADON - compute forward or reverse Radon transform or remove multiples
           by using the parabolic Radon transform to estimate multiples
           and subtract.						

     suradon <stdin >stdout [Optional Parameters]			

 Optional Parameters:							
 choose=0    0  Forward Radon transform				
             1  Compute data minus multiples				
             2  Compute estimate of multiples				
             3  Compute forward and reverse transform			
             4  Compute inverse Radon transform			
 igopt=1     1  parabolic transform: g(x) = offset**2			
             2  Foster/Mosher psuedo hyperbolic transform		
                   g(x) = sqrt(depth**2 + offset**2)			
             3  Linear tau-p: g(x) = offset				
             4  abs linear tau-p: g(x) = abs(offset)			
 offref=2000.    reference maximum offset to which maximum and minimum	
                 moveout times are associated				
 interoff=0.     intercept offset to which tau-p times are associated	
 pmin=-200       minimum moveout in ms on reference offset		
 pmax=400        maximum moveout in ms on reference offset		
 dp=16           moveout increment in ms on reference offset		
 pmula=80        moveout in ms on reference offset where multiples begin
                     at maximum time					
 pmulb=200       moveout in ms on reference offset where multiples begin
                     at zero time					
 depthref=500.   Reference depth for Foster/Mosher hyperbolic transform
 nwin=1          number of windows to use through the mute zone	
 f1=60.          High-end frequency before taper off			
 f2=80.          High-end frequency					
 prewhite=0.1    Prewhitening factor in percent.			
 cdpkey=cdp      name of header word for defining ensemble		
 offkey=offset   name of header word with spatial information		
 nxmax=240       maximum number of input traces per ensemble		
 ltaper=7	  taper (integer) for mute tapering function		

 Optimizing Parameters:						
 The following parameters are occasionally used to avoid spatial aliasing
 problems on the linear tau-p transform.  Not recommended for other	
 transforms...								
 ninterp=0      number of traces to interpolate between each input trace
                   prior to computing transform			
 freq1=4.0      low-end frequency in Hz for picking (good default: 3 Hz)
                (Known bug: freq1 cannot be zero) 
 freq2=20.0     high-end frequency in Hz for picking (good default: 20 Hz)
 lagc=400       length of AGC operator for picking (good default: 400 ms)
 lent=5         length of time smoother in samples for picker		
                     (good default: 5 samples)				
 lenx=7         length of space smoother in samples for picker		
                     (good default: 1 sample)				
 xopt=1         1 = use differences for spatial derivative		
                        (works with irregular spacing)			
                0 = use FFT derivative for spatial derivatives		
                      (more accurate but requires regular spacing and	
                      at least 16 input tracs--will switch to differences
                      automatically if have less than 16 input traces)	


 Credits:
	CWP: John Anderson (visitor to CSM from Mobil) Spring 1993

 Multiple removal notes:
	Usually the input data are NMO corrected CMP gathers.  The
	first pass is to compute a parabolic Radon transform and
 	identify the multiples in the transform domain.  Then, the
 	module is run on all the data using "choose=1" to estimate
 	and subtract the multiples.  See the May, 1993 CWP Project
	Review for more extensive documentation.

 NWIN notes:
	The parabolic transform runs with higher resolution if the
 	mute zone is honored.  When "nwin" is specified larger than
   	one (say 6), then multiple windows are used through the mute
 	zone.  It is assumed in this case that the input data are
 	sorted by the offkey header item from small offset to large
 	offset.  This causes the code to run 6 times longer.  The
      mute time is taken from the "muts" header word.
      You may have to manually set this header field yourself, if
      it is not already set.

 References:
 Anderson, J. E., 1993, Parabolic and linear 2-D, tau-p transforms
       using the generalized radon tranform, in May 11-14, 1993
       Project Review, Consortium Project on Seismic Inverse methods
       for Complex Structures, CWP-137, Center for Wave Phenomena
       internal report.
 Other References cited in above paper:
 Beylkin, G,.1987, The discrete Radon transform: IEEE Transactions
       of Acoustics, Speech, and Signal Processing, 35, 162-712.
 Chapman, C.H.,1981, Generalized Radon transforms and slant stacks:
       Geophysical Journal of the Royal Astronomical Society, 66,