traceRay

Description

traceRay is a utility for visualizing ray paths through a sound velocity profile (SVP). It takes an SVP file, models the water column as a series of constant velocity layers, and then traces a set of acoustic rays at specified outgoing angles. The tool then generates a PostScript plot of these ray paths, showing their trajectory (horizontal range vs. depth) through the water column.

This tool is useful for understanding sound propagation behavior in different oceanographic conditions and for visualizing how SVP variations affect ray bending.

Usage 

traceRay -pro <svp_handle> [-fishdep <val>] [-layerthick <val>] [-spacing <step> <start> <finish>] [-range <val>] [-depth <val>] [-verbose]

Arguments

| Option | Description | |—|—| | -pro <svp_handle> | Required. Base name for the sound velocity profile file. * Expected input: <svp_handle>.RAWPROF (default), <svp_handle>.svp (-simradsvp), or <svp_handle>.profile (another format). | | -fishdep <val> | Depth of the transducer/fish (meters). | 50.0 | | -layerthick <val> | Thickness of the constant velocity layers in the water column model (meters). | 20.0 | | -spacing <step> <start> <finish> | Defines the angular spacing for ray tracing: * step: Angular step (degrees). * start: Starting beam angle (degrees). * finish: Finishing beam angle (degrees). | 0.01 0 89 | | -range <val> | Maximum horizontal range for plotting (meters). | 22500.0 | | -depth <val> | Maximum vertical depth for plotting (meters). | 5000.0 | | -verbose | Enable verbose output. | | | -simradsvp | Input SVP file is in Simrad SVP format (.svp). | | -NEWsvp | Input SVP file is in a “NEW” raw format (.RAWPROF). |

How It Works

  1. Initialization: Parses command-line arguments, setting various ray tracing and plotting parameters.
  2. SVP Reading (read_in_*() functions):
    • Opens the input SVP file specified by -pro and the format flags (-simradsvp, -NEWsvp).
    • Calls one of the read_in_raw, read_in_NEW_raw, or read_in_svp functions to load the raw sound velocity profile data (rawvel, rawdep).
    • If std16_flag or NEW_flag is set, make_equisvp() is called to interpolate the raw SVP into an equi-spaced layered model (veldep).
  3. Plot Setup:
    • Initializes a plotlib PostScript output (svp_plot.meta).
    • Sets up plot dimensions (dx, dy), X/Y axis ranges (xmin, xmax, ymin, ymax), and labels (vellabel, depthlabel, rangelabel).
    • Draws the main plot frame and legends.
    • Plots the sound velocity profile (velocity vs. depth) as a line in a dedicated panel.
  4. Ray Tracing Loop:
    • Iterates through each outangle from startangle to finishangle with anglestep.
    • For each outangle:
      • Initializes posx, posz, ttime, and rangle.
      • Sets the initial pen position for plotting the ray.
      • Layer-by-Layer Propagation: Traces the ray through the water column layers:
        • Updates posx, posz, and ttime based on the ray’s path through the current layer’s velocity.
        • Converts posx and posz to screen coordinates (xpos, ypos).
        • Draws a line segment from the previous point (oldxpos, oldypos) to the current point (xpos, ypos), visualizing the ray path.
        • Applies Snell’s Law to calculate the new rangle for the next layer.
        • Handles cases where the ray goes beyond maxrange or becomes horizontal.
  5. Cleanup: Closes the input SVP file and plotlib output.

Output Files

  • <svp_handle>.meta: A PostScript metafile (.meta) visualizing the SVP and the traced ray paths.

Dependencies

  • plotlib.h: For plotlib functions.
  • support.h: For general utility functions.
  • j_watercolumn.h: For water column structures and ray tracing functions.
  • math.h: For mathematical functions.

Notes

traceRay provides a powerful visualization of sound propagation through the water column. This is essential for understanding how SVP variations affect multibeam sonar performance, particularly beam bending and the resulting errors in depth and position. The PostScript output allows for high-quality figures suitable for analysis and presentation. The tool creates new files, preserving the original SVP data.