Index Database

In order for SEG-Y Reader to efficiently process large 3D SEG-Y files, the SEG-Y Reader must scan the entire file to determine the extents of the survey and the ranges of values within it. This information is stored in the Index Database, named <SEG-Y Filename>.index.gdb. 

In order to scan the file, the SEG-Y file must be properly configured and a configuration file must be generated. If the configuration file already exists in the current working directory, it will be automatically loaded when the SEG-Y file is loaded.

If the configuration is valid, the options under SEG-Y Config will be disabled and options under Process SEG-Y will be enabled.

When you click Process SEG-Y for a configured 3D survey, it first verifies that the configuration is valid, then scans the entire file to determine the number of and locations of traces within the file. This information is stored in the Index Database, named <SEG-Y Filename>.XML.   Each line in the Index Database represents one Line in the survey, based on the Inline channel specified in the configuration. Traces that do not have Inline/Crossline information are dumped in Line 0 of the database.

Information stored in the Index Database includes the X, Y, Inline, Crossline, and two mask channels, plus offsets to the traces for quick random access of the file later.  If a valid configuration file and an Index Database exist in the same directory as the SEG-Y file, SEG-Y Reader will automatically load both. You may then export the file with minimal processing. 

You can load the index GDB into Oasis montaj to plot it, or mask traces in the survey.  This does not affect the size of the final database or voxel, but will dummy some of the traces within it.