Topic:
How to load multiple offset surveys.

Description:
Certain processing types, like AVO require multiple iterations of a survey to be
loaded.  Because they are different processings of the same survey, often the
contractor will write the data to tape where all the first inlines occur as
separate traces, followed by all the second inlines, etc and this can be a
challenge to load.        

Solution:
In the following example, each processed data is being loaded to a separate
survey on tape.

On tape, there are 3 surveys to load:
Inline 1/survey 1, followed by inline 2/survey 2, etc on each consecutive trace,
that cdp range is 6884 - 7978 and inline range is 1640 - 4820.  When you segy
dump the data starting with trace 1, looks something like this:
    		line     cdp
		1640    6884
		1641	6884
	      	1642	6884
		1640	6886
The cdp increment is 2 (from the segy dump), and can be read from the trace
header.  Also note that the last digit in the line number refers to which survey
the line should be loaded(0, 1, or 2).  Look for some relationship like this in
your dataset.

1.) You will need to set your trace decimation to 3. In IESX Data Manager >
    Seismic > Load seismic > User defined 3D > Define storage > Load every nth
    trace = 3.  Input inline numbers 164 - 482 (truncate the last digit in this
    case, because it will stop after one trace if you don't). When you set the
    cdp range, be sure that the ending cdp is divisible by the increment, or it
    will not finish loading the line.  The last cdp in this dataset is 7978, and
    it will not load the last cdp until it is set to 7980 or more. Set the other
    parameters for your dataset.

2.) Select 'Define input format'and set your line number to be read from
    expression. Since the last digit in the line number is referring to which
    survey the line belongs to, the following expression will be used to load
    line number: trunc (ln/10).  For the first survey, start your load at trace
    1, for the second survey, start at trace 2, and for the third survey, start
    at trace 3. Also, recommend setting bypass on integrity check, line header
    location set to all tapes and trace/line format to variable.    

					



Last Modified on: 31-AUG-99