revision

这是用matlab对segy数据进行处理

1.2  : January 07, 2008
       Updated GUI to work for Matlab R2008a
       enabled loading of partial segyfile (using time and header ranges)
       from GUI (ctrl X)
       enabled editing of the textual file header (both ASCII and EBCDIC)

1.11 : August 2008
       Kristian Stormark (<[e-mail]>) contributed a change 
       to GetSegyTraceHeader that reduce the number of discoperations 
       causing a significant speed up 

1.08 : March 2007
       Urs Boeniger contributed a patch that allows arbitrary 
       SegyTraceHeaders to be specified for WriteSegy.m

1.06 : FIxed a bug taht casue a fixed length of 5011 samples in ReadSu

1.02 : Cleaning up code to work with Octave 2.1.57

1.01 : 'jump' related fixes

1.00 : Cleaning up some Matlab 7.0 specific bugs. 

0.99 : Just cleaning up to prepare for a release 1.0

0.93 
     ReadSegy : RAM is preallocated, causing a significant speed up 
     when reading large files (>30%)

0.92 April 13, 2004
     DUE TO A BUG IN MATLAB 6.5 : Technical Solution Number: 31977,
     writing of segy files did not work in some windows version of
     matlab 6.5. A workaround have been implemeneted. 
     fseek(segyid,'bof',0) did not always work ?
     
     disp statements have been replaced with SegymatVerbose, making
     it easier to control verbose output to the screen. The verbose level
     can be set in SegymatVerbose.m

     CheckSegyTraceHeader has been implemeneted as an m-file of its own.
     It was a part of PutSegyTrace but slowed down writing of segy files
     considerably. Now it is only run if you edit the m-files that write 
     data to disc. This change gives great speed improvement.


0.91 Nov 21, 2003: 
     Strange bug when using ReadSegy on one platform : 
"At compilation SkipData was an undefined variable or function.>> >> >> >> >> Function SkipData is now in context.  To use a function that is>> >> >> >> >> not in context at compilation use FEVAL or EVAL.
"
     Could not reprodice the error using the same SGY file on either Linux or Windows.

0.90 : 
     GUI is reimplemented.
     Coded is prepared to be compiled.
	
     Support For Extended Textual File Headers.


0.45 : 
     WriteSegy : 'dt' was always reported as not set, even if it were.
                 It did not affect the written SEGY file though.

0.44 : 
     ibm2num : simpler error message when transformation fails.

0.43 : June 19, 2003
     ReadSegy : Crashed when SegyHeader sais Rev0 and DFS=5, since
     DFS=5 is not defined for Rev0. Now, if DFS=5 is chosen Revision
     is automatically set to 1.

0.42 : 
     GUIEditSegyHeader : Updated to handle the complete SegyHeader (30/03/2003)
     GUIEditTextualFileHeader : Updated to give warning when wrong format is chosen.
     ReadSegy : Rev0, data sample format 2 and 3 are now set to 2 and 4 byte signed integers.

0.41 : 
     ReadSegy : Fixed bug that caused ReadSegy to crash when no data was returned.

0.40 : Jan-22-2003
     ReadSegy : -fixed 'endian' big introduced in version 0.39
	        -Implemented more robust reading of traces with varying trace lengths
		Now the code will not stop running, simply return an error message.
		- re-implemented the 'SkipData' option that somehow had been removed from the code

     ReadSegyHeader : fixed 'endian' big introduced in version 0.39

0.39 : Jan-20-2003
	
     ReadSegy : option to read little endian formatted data

     ReadSegyHeader : Reads only the Segy Binary Header	

     ReadSuFast/ReadSegyFast
     If headers are not required, fast version of the reading algorithms
     is now available. These are up to 20 times faster.
     
     EBCDIC support
     
     GUIEditTextualFileHeader
     GUI to display/edit the Textual Segy Header in EBCDIC/ASCII format.
   
     
     

0.38 : September 6-2002
     WriteSegy : takes options 'revision' and 'dsf'
	         to set SEG-Y revision number and 
		 Data Sample Format
     WriteSegyStructure :
		 takes options 'revision' and 'dsf'
	         to set SEG-Y revision number and 
		 Data Sample Format
     ReadSegy : Takes option 'dsf' to force DataSamplingFormat
	        SegyHeader.FixedLengthTraceFlag is no longer forced to be 1 !

     Thus now all Read and Write routines takes the options
     'revsision' and 'dsf'

     SegyHeader: Two fields were added that contains unassigned header values
	 SegyHeader.Unassigned1 : byte 3261-3500
	 SegyHeader.Unassigned2 : byte 3507-3600 

     SegyTraceheaders : Added two fields for unassigned values :
	 SegyTraceHeader.UnassignedInt1 : int32, Byte 232+4	
	 SegyTraceHeader.UnassignedInt1 : Int32, Byte 236+4	

0.37 : August 23-2002
     Format of dt and ns changed to unsigned integers.

0.36 : August 15-2002
     ReadSegy was corrupted in 0.35. Bug Fix release.	 


0.35 : June 16-2002
     Correct DayOfYear in PutSegyTrace.m, 
     - thanks to Michael Toews ([e-mail])
     Minor bugfixes. Released as a release on Sourceforge.

0.33 : June 03-2002
      Added Rading and writing SU and SEGY to GUI.
	
0.32 : May 15-2002
      Colormaps and gain control is added.

0.31 : May 04-2002
      GUI Segy Reader useable.

0.3 : May 01-2002 
      Added fascility to read in parts of a SEG-Y file

0.2 : Added 'SkipData', so that only header values are read

0.1 : Initial release