Topic:
Detailed description of how to load a 3d survey.

Description:
        

Solution:
Given the perfect scenario, have all the proper paper work and the perfect data,
here are general instructions on how to load a 3D survey.  

IESX requires the 3D survey to be "rectangular".  If the primary lines have
varying numbers of traces, IESX will "pad" traces (actually dummy traces) to
make the survey appear rectangular.  

Recommended Data Loading Sequence:

1)  Create a Project (if necessary)

2)  Examine the tapes (use SEGDUMP) to verify the following:
    Is the tape readable?
    Is the line number(s) present?
    Is the cdp number present and in what header location?
    Is the cdp increment positive or negative?
    Is the cdp increment less than 1, greater than 1?
    What happens to the cdp number at the start of the next line?
    Is the sample rate correct (should be in microseconds)?
    Is the number of samples correct?

3)  Test load several 3D lines

4)  Enter the Seis3DV and display a few lines.
    Check to see if the lines begin and end at the correct traces.
    If traces were padded, was it done correctly?
    Verify the integrity of the seismic trace data.
    Display a few cross-lines.

5)  Select Basemap from Applicatoin
    Select & Display several lines (inline and cross-lines) from the basemap.
    Define a traverse on the basemap.
    Check the geometry of the basemap.
    Verify that the x,y coordinates for the map are correct.  Are you in the
    right part of the world?

6)  Load the remainder of the survey.
    Note: The user may wish to determine the disk space requirements for the
    survey prior to loading.

 

Things you want the vendor to supply you with:

1) A data loading sheet with the inline & cdp range that is on the tape, the
   byte location for the line number and cdp, what the inline & cdp increment
   by and the end time of the data.  Are these multiple lines per file or single
   line per file ?(usually multi line per file)

2) 3 points for the survey which include either x,y or lat/long and the 
   inline & cdp at each of these points. 

3) A scaled map of the data on the tape (for qc purposes)

How to SEGY dump seismic data:

1)   If you want to see what is on a tape, or file, you can do a SEGY dump by
     pressing the 'SEGY dump...' button.  

2)   The 'SEGY dump' window comes up.
     Toggle the appropriate type of dump, either disk file or tape. 
     If disk, enter the complete directory structure and file name in the box
     marked "Input disk file"

3)   Toggle 'Trace header' to 'Full'

4)   Enter 'End range' to something small like, 1.00

5)   If you were given the byte location for Inline & CDP and you want to varify
     it, If you press the 'Trace header locations...' button, you can enter
     those values there and set the 'Format' type to IBM(32 bit int.) and press
     the O.K. button when done.  Once you are back at the 'SEGY dump' window,
     press the 'Dump...' button at the bottom.

     ** A note, it is not neccessary to setup the byte range for Inline & CDP in
       order to do a dump of the SEGY tape or file.  This is helpful to use if
       your information is past byte 118 in the trace header where you can't
       see.

Example of standard SEGY format:

SEG-Y Format           
                                        SEGY Record Layout
______________________
|                     |               (* - records for which # of bytes is
|                     |                 mandatory)
|                     |
|                     |               EBCIDIC reel header *-comment records
|   3200 bytes        |               (this record must be present but is not 
|_____________________|  ------------  retained after the line is loaded)
|_____________________|---- used for tape positioning (not present in disk file)
|                     |
|                     |
| 400 bytes           |  ------------ binary line header *-information regarding
|_____________________|               this trace (this info. is used & retained)
|_____________________|
|                     |
| 240 bytes           | ------------ binary trace header - information regarding
| -----------------   |              this trace (this info. is used & retained)
|  samples for        |
|  trace 1            |
|_____________________|
|_____________________|
|                     |
|  240 bytes          |
|  ----------------   |
|   samples for       |
|   trace 2           |
|                     |
|_____________________|
|/////////////////////| --------- End of File marker (EOF) one at the end
|---------------------|           of each file

|---------------------|
|/////////////////////| --------- End of Tape marker (EOT) - two EOF's mark
|---------------------|           the end of the tape



How to set up the loading definition:

1)  In the Application Manager go to Seismic - the IESX Session Manager will
    come up.

2)  Application > Data Manager > Seismic/Load seismic ...

3)  The 'Load seismic trace data' window comes up

4)  Toggle 'Loading mode' to 'User defined 3D'

5)  Click on 'Define storage ....' The 'Define 3D seismic storage parameters'
    window comes up.

6)  Click on 'Survey...' - The 'Select/create a survey' window comes up.

7)  Press the 'Create...' buttom at the bottom - The 'Select/create a survey'
    window comes up.

8)  Here you will enter a Survey name and description.- O.K. The 'Create 3D
    survey with locations' window comes up.

9)  Select the type of 'Units', 'Location entry type', 'Angles defined as' 
    If the 3 points you are using to define the survey are different then the
    project, you would press the 'Survey projection ...' button at the top,
    right corner.

10)  Now enter your 3 points in the following boxes. When done, press 'Apply' to
     create the survey.

11)  Back at the 'Define 3D seismic storage parameters' window, Press the
     'Class...' button. The 'Select/create a class' window comes up.

12)  Press the 'Create...' button at the bottom. A 'Create a class' window
     comes up.  Enter a class name and/or description.  When done, press the
     'Add' button at the bottom.
  
13)  Now you are back at the 'Define 3D seismic storage parameters' window. The
     first time you go to load your surveys, you should only try to load a few
     lines (lets say 10), just to see how it goes, after you are sucessful at
     loading those, then you can continue with the rest of the tape(s).
     Enter the first inline under, 'First inline number'. Enter 'Last inline
     number' or if you are checking for the first time, enter up to 10 lines. 
     Enter 'Start line at input CDP'
     Enter 'End line at input CDP' 
     Enter 'Load every Nth TRC' (usually 1)
     Enter 'End time to load' (remember, you don't have to load the full time
     range on the tape if you don't need to) - Then press the O.K. button at the
     bottom.

14)  Now you are back at the 'Load seismic trace data' window. Click on the
     'Define input format ...' button. The 'Define 3D input data format' window
     comes up.

15)  Set format specification:
     Toggle 'Seismic format' to: SEGY
     Toggle 'Line/file' to: Multiple
     Toggle ;Traces/line format' to Variable
     Toggle 'Line number' to Trace header
     Toggle 'CDP number' to Trace header
     Toggle 'SP (Shot point) number' to Expression

16)  Header locations:
     Enter the Start byte for 'Line number' as given on data sheet from vendor
     Enter the Start byte for 'CDP number' as given on data sheet from vendor
     Enter the Start byte for 'SP number' to blank
     Enter the Start byte for 'Time of first sample' to blank
     Toggle 'Format' for 'Line number' to 'IBM(32 bit int.)'
     Toggle 'Format' for 'CDP number' to 'IBM(32bit int.)'
     Toggle 'Format' for 'SP number' to 'No selection'
     Toggle 'Format' for Time of first sample' to 'No selection'

     Click on 'SP,CDP and line number expressions...' button, the 'Define 3D
     shot point, CDP and line number expressions' window comes up.

     You will see a --> beside SP =
     In that box, type CDP so that SP=CDP, then press the O.K. button at the
     bottom

17)  You are now back at the 'Define 3D input data format' window.
     If you are loading your data from tape, toggle 'Data source' to 'Tape'
     If you are loading your data from disk, toggle 'Data source' to 'Disk'

      If you toggle 'Data source' to Disk, you will need to define disk files
      under the 'Define disk file(s)....' button. The 'Define file(s) window
      comes up.  Here type the complete directory structure where the file is,
      including the file name.
      Example: /home/disk1/user/tape1.segy

      After entering each directory and file, press the 'Add' button.  When
      done, press the O.K. button.

      If you toggled 'Data source' to Tape, you will need to define your tape(s)
      under the 'Define tape(s)....' button. The 'Define tape(s)' window comes
      up.  Here you can enter anything for a tape name. Many times the vendor
      actually has a tape number of the tape, you can use that if you like, or
      you might give it names like tape1, tape2, etc.  Most people can only load
      1 tape at a time, so they just enter a 1 for name.  After entering a name,
      press the 'Add' button.  When all done, press the O.K. button.

18)  You are now back at the 'Define 3D input data format' window.Once
     everything has been setup, press the O.K. button at the bottom.

19)  You are now back at the 'Load seismic trace data' window. If you are happy
     with your loading definition, it is a good idea to save this format for
     later use, or to refer to for a later time. 

20)  To save, press the 'Save as...' button. The 'Save loading definition'
     window comes up.  Here enter a name and/or descrition for your loading
     definition.  Then press the O.K. button.

21)  You are now back at the 'Load seismic trace data' window.

22)  Select 'Load...' to start loading seismic data.

23)  If after loading a few lines, all looks well, then you can modify your
     loading definition to cover the rest of the data to load, pointing to the
     appropriate disk file(s) or tape(s), making sure to save the loading
     definition in the end.




Last Modified on: 21-JAN-00