SUWIND - window traces by key word					

     suwind <stdin >stdout [options]					

 Required Parameters:							
	none								

 Optional Parameters:							
	verbose=0	=1 for verbose					
	key=tracl	Key header word to window on (see segy.h)	
	min=LONG_MIN    min value of key header word to pass		
	max=LONG_MAX    max value of key header word to pass		
	abs=0	   =1 to take absolute value of key header word		
	j=1	     Pass every j-th trace ...				
	s=0	     ... based at s  (if ((key - s)%j) == 0)		
	count=ULONG_MAX ... up to count traces				
	reject=none     Skip traces with specified key values		
	accept=none     Pass traces with specified key values(see notes)
			processing, but do no window the data		
 Options for vertical windowing (time gating):				
	dt=tr.dt (from header)  time sampling interval (sec)		
	tmin=0.0		min time to pass			
	tmax=(from header)	max time to pass			
	itmin=0		 min time sample to pass			
	itmax=(from header)     max time sample to pass			
	nt=itmax-itmin+1	number of time samples to pass		

 Notes:								
	On large data sets, the count parameter should be set if	
	possible.  Otherwise, every trace in the data set will be	
	examined.  However, the count parameter overrides the accept    
	parameter, so you can't specify count if you want true		
	unconditional acceptance.					

	The accept option is a bit strange--it does NOT mean accept ONLY
	the traces on the accept list!  It means accept these traces,   
	even if they would otherwise be rejected (except as noted in the
	previous paragraph).  To implement accept-only, you can use the 
	max=0 option (rejecting everything).  For example, to accept    
	only the tracl values 4, 5 and 6:				
		... | suwind max=0 accept=4,5,6 | ...		   	

       Another example is the case of suppressing nonseismic traces in 
       a seismic data set. By the SEGY standard header field trace id, 
       trid=1 designates traces as being seismic traces. Other traces, 
       such as calibration traces may be designated by another value.  
      	Example:  trid=1 seismic and trid=0 is nonseismic. To reject    
       nonseismic traces						
	       ... | suwind key=trid reject=0 | ...			

	On most 32 bit machines, LONG_MIN, LONG_MAX and ULONG_MAX are   
	about -2E9,+2E9 and 4E9, they are defined in limits.h.		

	Selecting times beyond the maximum in the data induces		
	zero padding (up to SU_NFLTS).					

	The time gating here is to the nearest neighboring sample or    
	time value. Gating to the exact temporal value requires	 	
	resampling if the selected times fall between samples on the    
	trace. Use suresamp to perform the time gating in this case.    

	It doesn't really make sense to specify both itmin and tmin,	
	but specifying itmin takes precedence over specifying tmin.	
	Similarly, itmax takes precedence over tmax and tmax over nt.	
	If dt in header is not set, then dt is mandatory		




 Credits:
	SEP: Einar Kjartansson
	CWP: Shuki Ronen, Jack Cohen, Chris Liner
	Warnemuende: Toralf Foerster

 Trace header fields accessed: ns, dt, delrt, keyword
 Trace header fields modified: ns, delrt, ntr