fixEM3K_V3

Description

fixEM3K_V3 is a specialized utility designed to correct a specific data format issue in early Simrad EM3000 (and EM3002) multibeam sonar data files that were written in version 3 of the OMG-HDCS format. This issue arose because the profile header size was updated to include additional runtime telegram information, but existing files did not reflect this change, leading to incorrect parsing.

This tool essentially “pads” the profile header of affected files and sets a flag (maxProcDepth to non-zero) to indicate that the fix has been applied, distinguishing them from uncorrected files.

Usage 

fixEM3K_V3 <old_V3file> <fixed_V3file> [-v]

Arguments

Option Description
<old_V3file> Required. The path to the input, uncorrected EM3000/EM3002 V3 merged file.
<fixed_V3file> Required. The path for the output corrected EM3000/EM3002 V3 merged file.
-v Enable verbose output.
-first <ping_num> / -last <ping_num> (Present in USAGE but not implemented) These options likely intended to specify a ping range, but main processes all profiles.

How It Works

  1. File Opening: Opens the old_V3file for reading and the fixed_V3file for writing.
  2. Summary Header Check:
    • Reads the OMG_HDCS_summary_header from the old_V3file.
    • It verifies that summary.fileVersion is 3 and that summary.maxProcDepth is 0 (indicating an uncorrected file). If these conditions are not met, it exits with an error.
    • Sets summary.maxProcDepth to 1 to mark the file as fixed.
  3. Summary Header Writing: Writes the modified summary header to the fixed_V3file.
  4. Profile and Beam Data Copying: Iterates through each profile in the input file:
    • Reads a portion of the profile header (all but the last 24 bytes, which were missing in the old V3 format) into a bulk_data buffer.
    • Writes this bulk_data to the fixed_V3file.
    • Writes 24 bytes of extra_bytes (initialized to zeros) to the fixed_V3file, effectively padding the profile header to its correct size.
    • Reads the entire block of beam data for the current profile into bulk_data.
    • Writes this beam data to the fixed_V3file.

Output Files

  • <fixed_V3file>: A new OMG-HDCS merged file with corrected profile header sizes.

Dependencies

  • OMG_HDCS_jversion.h: For OMG-HDCS data structures.
  • support.h: For general utility functions and error handling.

Notes

This tool addresses a very specific historical data format issue. It’s crucial for ensuring that early EM3000/EM3002 data in OMG-HDCS version 3 format can be correctly parsed by other tools. The tool creates a new file rather than modifying in-place, which is safer. The first and last ping options are noted as not implemented, meaning it always processes the entire file.