Defining 2D 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 crucial information is extracted from the headers of  the SEG-Y file.  

How do I define keywords when loading 2D 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 2D lines, you must define keywords for:

• CDP
• Shot Sequence Number (shot point)
• Coordinate X
• Coordinate Y

1. Click  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 CDP keyword. The CDP number normally increases by 1 as the trace number increases by 1. 
   
   
1. Scroll through the traces to find the CDP by using the slider () or by using the arrows next to the slider.
   
2. Click on the CDP 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. Click  to graph all traces in the file.
   
   
5. Check that the graph has a constant slope and resembles this sample graph. 
   
   
6. Close the graph. If think you've correctly identified the CDP continue to the next step, otherwise repeat steps i. to v. until you've located the CDP. Remember that you may need to switch the Format if you can't find the right value.
   
   
7.  Click on the key icon  . This opens the Add Keyword window.
   
   
   
   
   
   
8. From the drop-down list beside Key Name, select "CDP Number" and click . You will now see the keyword defined on the right hand side of the SEG-Y Viewer.
   
   
5. Define the Shot Sequence Number keyword using the steps listed above. The Shot Sequence number usually increments by 0.5. Because some formats do not store decimals, the shot sequence might increase by an integer value, for example, 50 or 500. If this is the case you'll need to apply a Scale Factor in the Add Keyword window. (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. (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 to the file name.
   
   
10. Close the SEG-Y Viewer.