mergeSB2K

Description

mergeSB2K is a utility designed to merge SeaBeam 2000 sidescan data (from GLORIA-format files) onto existing OMG-HDCS (.merged) bathymetry files. It essentially adds a reference to the corresponding sidescan data within the beam structures of the .merged file, allowing other OMG tools to access and display the sidescan imagery alongside the bathymetry.

This tool is useful for integrating sidescan data, which provides valuable information about seabed texture and features, with multibeam bathymetry for a more complete understanding of the seafloor.

Usage 

mergeSB2K -ss <tidefile> <mergefile(s)> [-v] [-date <year> <month> <day>] [-base_offset <value>]

Arguments

Option Description
-ss <tidefile> Required. Path to the GLORIA-format sidescan file (named tidefile due to historical reasons, likely containing time-indexed sidescan records).
<mergefile(s)> Required. One or more OMG-HDCS .merged files to which the sidescan data will be merged.
-v Enable verbose output.
-date <year> <month> <day> (Optional) Manually set the reference date for the summary header in the .merged file. This can be useful if the timestamp in the .merged file’s header is incorrect or missing.
-base_offset <value> (Optional) Sets an integer base offset (in millimeters) to be added to the tide value. Used for tide correction (historical name).

How It Works

  1. Initialization: Parses command-line arguments to get the sidescan (GLORIA) file path, input merged files, and optional parameters (verbose_flag, year, month, day, base_offset).
  2. GLORIA File Opening: Opens the GLORIA-format sidescan file (tidefile) for reading.
  3. Merged File Processing Loop:
    • For each input .merged file:
      • Opens the file in read/write mode (r+).
      • Reads the OMG_HDCS_summary_header. If a -date is provided, it updates summary.refTime in the header and writes it back to the file.
      • Profile Iteration: Iterates through each profile (ping) in the merged file:
        • Reads the OMG_HDCS_profile_header.
        • Calculates the absolute time (time) of the current profile.
        • Sidescan Record Search: Uses jcu_time_search() to find the closest matching sidescan record in the GLORIA file based on time.
        • Reads the gloria_rec (sidescan record) from the GLORIA file.
        • Beam Data Update: Reads the existing OMG_HDCS_beam array for the current profile. It then updates specific fields of beam 61 (hardcoded index) in the beams array:
          • beams[61].offset: Set to the file offset of the sidescan data within the GLORIA file.
          • beams[61].no_samples: Set to the number of samples (fixed at 1024).
          • beams[61].centre_no: Set to the center sample (512).
          • beams[61].sample_interval: Set to the pixel size from the GLORIA header (tide_rec.header.pixel_size).
        • Writes the modified OMG_HDCS_beam array back to the .merged file.
      • Closes the current .merged file.
  4. Cleanup: Closes the GLORIA file and exits.

Output

The input .merged files are modified in-place. The OMG_HDCS_beam structure for beam 61 (a specific placeholder beam) in each profile is updated with references (offset, sample count, etc.) to the corresponding sidescan data within the GLORIA file.