make_motionTS

Description

make_motionTS is a utility designed to generate synthetic time-series data for vessel motion (roll, pitch, heading, heave). It allows users to define various “motion packets,” each specifying a type of motion, its duration, period, and peak amplitude. The tool then superimposes these sinusoidal motion components to create a composite motion time series, which is output to an ASCII file.

This tool is useful for creating controlled test data for Quality Control (QC) purposes, such as testing motion compensation algorithms or analyzing the response of processing routines to specific types of vessel motion.

Usage 

make_motionTS [-v] [-roll <start_time> <stop_time> <start_period> <stop_period> <peak_amplitude>] [-pitch ...] [-heading ...] [-heave ...]

Arguments

| Option | Description | |—|—| | -roll <start_time> <stop_time> <start_period> <stop_period> <peak_amplitude> | Defines a sinusoidal roll motion component. Parameters are: * start_time: Time (seconds) when this motion starts. * stop_time: Time (seconds) when this motion stops. * start_period: Period (seconds) of the sinusoidal motion at start_time. * stop_period: Period (seconds) of the sinusoidal motion at stop_time. * peak_amplitude: Maximum amplitude (e.g., in degrees for roll/pitch/heading, meters for heave). | | -pitch | Same parameters as -roll, but for pitch motion. | | -heading | Same parameters as -roll, but for heading motion. | | -heave | Same parameters as -roll, but for heave motion. | | -v | Enable verbose output. | |

How It Works

  1. Initialization: Parses command-line arguments to define motion_packet structures. It supports multiple motion_packet definitions for various types of motion.
  2. Time Series Generation:
    • Initializes a motion_sample array (timeSeries) of numSECONDS * perSECOND elements (currently 600 seconds with 10 samples/second, totaling 6000 samples).
    • Each motion_sample has fields for time, roll, pitch, heading, and heave.
    • For each defined motion_packet:
      • It iterates through the timeSeries array.
      • If a sample’s time falls within the start_time and stop_time of the packet:
        • It calculates a sinusoidal value based on the packet’s peak_amplitude and a phase derived from time, start_time, and start_period.
        • A cosine-squared taper is applied to the value to smooth the onset and offset of the motion.
        • This value is added to the corresponding motion component (roll, pitch, heading, or heave) in the timeSeries array.
  3. Output: Writes the generated timeSeries to an ASCII file named fake.ts. The output format is: 
    <total_number_of_samples>
<time> <roll> <pitch> <heading> <heave>
...
  4. Cleanup: Closes the output file.

Output Files

  • fake.ts: An ASCII text file containing the generated synthetic time series data.

Dependencies

  • support.h: For general utility functions.
  • math.h: For mathematical functions.

Notes

This tool is particularly valuable for controlled testing and validation of motion compensation algorithms. By generating synthetic motion with known characteristics, it allows for rigorous assessment of processing routines without the complexities of real-world noise and unpredictable motion patterns. The cosine-squared taper helps create smooth transitions for the onset and offset of motion components.