Topic:
Simplest method of dumping many consecutive 2d lines from one SEG-Y tape. 

Description:
This procedure is useful for tapes that have multiple 2D lines, but no
information about what is on the tape.  You ave to dump all the files to
determine the line names and SP/CDP relationships.       

Solution:
This method is fast, and will output files with:
 - The EBCDIC Header (which almost certainly contains the line name)
 - SP and CDP for each trace        
Use the and "Tape rewind = No" option of "SEG-Y Dump..." to
facilitate dumping many consecutive 2D lines.


1. You will need to know which header words contain the SP and CDP numbers.  
   If the lines are all on one tape, you should only have to dump the first
   file to find out where the SP and CDP values are written to the header,
   assuming the header locations will not change from file to file.


2. When you have determined which header words contain SP and CDP numbers:

   From IESX> Data Manager> Load Seismic> SEG-Y Dump..., there is an option to    
   specify the format of any header words under "Trace Header Locations...".

   From the "SEG-Y Dump..." menu, click on  "Trace Header Locations...".
   Under the "Shot Point Number" parameter, set Start Byte to the header word  
   containing the SP, and Format to => IBM (32 bit int.).  
   Under the "CDP Number" parameter, set Start Byte to the header word 
   containing the CDP, and Format to => IBM (32 bit int.).  
   Blank out the "Start byte" fields for 
   "Time of First Sample", "Station location X/lon", "Station location Y/lat".   
   Click on "OK".


3. In IESX => DataManager => Load Seismic => SEG-Y Dump => 
   - Toggle on "Dump tape" 
   - Specify your tape drive
   - Set "Tape rewind" to "No"
   - Make sure "Skip tape files" is set to "0" 
               "Trace Header" is set to "None"
               "End Range" is set to "8"    
               "Output media" is set to "File".

   Under "Output file", put in the name of the file you want to create when 
   you dump the first file (~/tape1file1.dump will create a file called   
   tape1file1.dump in your login directory)


4. Now you are ready to dump.  
[Follow the procedure described below until you reach the end of tape]
    
    i)   Click on "Dump..."
    ii)  When the dump has finished, change the "Output file" name
           (for example: from ~/tape1file1.dump to ~/tape1file2.dump)
    iii) Repeat steps i and ii

The files will contain the EBCDIC header, the SP and CDP information, a minimum
of the other, seldom used information generally created when a tape is dumped.




Last Modified on: 06-OCT-00