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Loading 3D seismic can be a time consuming job, and it is very important that the import settings are correct before starting (to avoid having to do the job again). Therefore, 3D import is usually performed by first setting the import settings, and then performing a scan on the very first inlines only. This is achieved by leaving the Min/Value Inline setting at From file, but setting the Max setting to 10 lines higher than the first inline. This means you have to know the start value of the Inline. You should be able to find this in the Trace header or the EBCIDIC header.
Follow the #Scanfile guide explained for 2D seismic as it is almost identical to 3D seismic
Inline and Crossline byte position
If the Min and Max values for Inline or Crossline looks odd, the byte position could be wrong. The default byte positions in the SEG-Y 3D import is 5-8 for Inline and *21-24 for Crossline in the trace header, but in some cases this is not always correct. If the byte position is wrong try the following:
- Look for information about the Inline/Crossline byte position in the EBCIDIC header.
- Select the Trace header tab to view the SEG-Y file's headers trace by trace. The byte positions' values are continuously reported as you move through the file. By closely observing how the values change you should be able to determine the correct byte position.
Use the Inline/Crossline, Byte pos. spinbox to set the appropriate byte position.
Coordinates, interval and scaler
Make sure the X coordinate has 6 digits and that the Y coordinate has 7 digits. The coordinate Interval often gives us a good indication of if the coordinate is set correctly, as most seismic cubes have an interval of 12.5, 25, 50 meters or similar.
In some cases the scaler may be wrong, causing the X and Y values to have to few or to many digits. This can be adjusted by changing the scaler multiplication factor.
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The SEG-Y format states that a negative Scaler denotes division, e.g. Scaler = -10 means divide X and Y with 10. Geocap, on the other hand, uses pure multiplication, e.g. Scaler = 0.1 means multiply X and Y with 0.1. |
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The scaler may be 0 on file. This will lead to X and Y being 0 in the dataset. Fixing the Scaler to 1 is usually the correct setting in this case. |
Z(twt)-range and sample interval
The Z values are usually correct but you can have a look in the EBCIDIC header to see if there is any information about the sample interval or Z-range.
Import multiple files
Geocap lets you import multiple SEG-Y files in one go.