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Setting Geometry - Converting Observers' Logs to Trace Headers

There is an often unpleasant task called ``setting geometry'' which must be performed on field data. Often, a SEGY tape will have only a rudimentary set of header fields set in the data. The rest of the information (shot location, geophone location, etc...) will be supplied in the form of observers' logs.

For setting geometry, you may wish to dump a specific collection of header fields of interest into a file, read the file into a text editor or spreadsheet program so that you can make changes.

For example, if you have some file ``sudata'' which has some header fields set incorrectly or incompletely then the following command sequence illustrates a possible way of working with such data. You begin by reading the selected header fields into a file ``hdrfile''.

% sugethw < sudata output=geom key=key1,key2,... > hdrfile 		
Now edit the ASCII file hdrfile with any editor, setting the fields appropriately. Convert hdrfile to a binary format via:
% a2b < hdrfile n1=nfields > binary_file				
were ``nfields'' is the number of header fields in the ``key=..'' list above. Then load the new file of header fields via:
% sushw < sudata infile=binary_file key=key1,key2,... > sudata.edited
Again, ``key=key1,key2,...'' here is the same list as in the sugethw statement above. The finished product is the file sudata.edited.

If you are just beginning to set the header fields, you may build the ASCII header file ``hdrfile'' any way you want. This could be with your favorite text editor, or with a spreadsheet program. It is not important how the ascii file is created, as long as it is in multi-column ASCII format for the sequence above.

Of course, if you have the header values in a file consisting of C-style floats, (which you can make either from a C-program, or from Fortran data with ftnstrip) listed trace-by-trace, then you already have the ``binary_file'' and need only execute the final sequence.


next up previous contents
Next: SUCHW - Change (or Up: Setting, Editing, and Viewing Previous: SUSHW - Set the   Contents
John Stockwell 2007-04-10