Defining 3D Keywords

The SEG-Y File Viewer is used to examine SEG-Y files and to specify the location of certain critical keywords during data loading.

Defining keywords is one of the most important steps performed during data loading.  You need to define keywords so that crucial information can be extracted from the headers of  the SEG-Y file.  

How do I define keywords when loading 3D data?

You can use the  button to load a previously created Keyword file.  If you do not have an existing keyword file define you will need to create one. For 3D lines, you must define keywords for:

• Line Sequence Number (Inline)
• Trace Sequence Number (Crossline)
• Coordinate X
• Coordinate Y

1. Click  and to open the SEG-Y Viewer window.
   
   
2. Change the Data View to "Trace Header". The keywords are located in the Trace Header, however they can be in any of the available Formats.
   
   
3. Switch the Format until you see numbers that are recognizable. You will usually see the Keywords in Integer (32 bit), IBM floating-point, or IEEE floating-point formats.
   
   
4. Define the Line Sequence keyword. The Line Sequence Number increments at the end of every line after incrementing through every trace. The graph for this keyword resembles a staircase. As you scroll through the traces you are looking for a number that isn't changing.
1. Scroll through the traces to find the Line Sequence Number by using the slider () or by using the arrows next to the slider.
   
   
2. Click on the Line Sequence Number and ensure that the cursor is blinking within the number.  
3. Click the graph icon  at the top of the SEG-Y Viewer. This opens the Graph Header Word window. 
   
   
   
   
   
4. Enter a value of "5000" in the Last Trace Field. If you find that this doesn't show enough data in your graph you can increase this value.
   
5. Click  to graph the data.
   
   
6. Check that the graph looks like a staircase resembles this Sample Graph. 
   
   
7. Close the graph. If think you've correctly identified the Line Sequence Number continue to the next step, otherwise repeat steps i. to vi. until you've located the Line Sequence Number. Remember that you may need to switch the Format if you can't find the right value.
   
8.  Click on the key icon  . This opens the Add Keyword window.
   
   
   
   
   
   
9. From the drop-down list beside Key Name, select "Line Sequence Number" and click . You will now see the keyword defined on the right hand side of the SEG-Y Viewer.
   
   
5. Define the Trace Sequence Number keyword using the steps listed above.  The Trace Sequence Number increases by 1 until the Line Sequence Number increments, at which point the Trace Sequence Number drops to its starting point and begins increasing again. The graph for this keyword resembles a sawtooth. (Sample graph)
   
   
6. Define the Coordinate X and Coordinate Y using the steps listed above. These are usually located side by side, and are easy to recognize. If you don't see values that look like the coordinates in your project, try changing the Format . Because some formats do not store decimals, the coordinate values may contain an extra  digit. If this is the case you'll need to apply a Scale Factor in the Add Keyword window. The graphs for these keywords may resemble stairs or saw teeth. (Sample Graphs)
   
   
7. When all four keywords are defined, and appear in the right hand side of the SEG-Y Viewer, check that they are defined correctly, with appropriate values and decimal places.
   
   
8. From the File menu, select Save Keywords As.  
   
   
9. Enter a Keyword file name that you will remember and click .  The .kwd extension is added to the file name.
   
   
10. Close the SEG-Y Viewer.  
    
    

If you can't locate all four keywords you may need to use the Advanced Trace and Line Description dialog, or the Specify Geometry dialog.