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Tide compensation#

Compensate varying tidal elevations that might occur during seismo-acoustic surveys.

Description#

The tidal elevation (and thus deviation from the mean sea level) is predicted using the tidal constituents based on the TPXO9-atlas models provided by Gary Egbert & Svetlana Erofeeva from the Oregon State University (available on request for academic purposes).

To derive an individual tidal elevation for each shotpoint (and time) the Python package tpxo-tide-prediction is utilized that allows to compute the required tidal information for each shotpoint (i.e. timestamp) of a seismo-acoustic profile.

For more information refer to the GitHub project page.

Vertical offset of individual TOPAS profiles caused by varying tidal elevation Vertical offset of individual TOPAS profiles caused by varying tidal elevation

Figure 1: Vertical offset of individual TOPAS profiles caused by varying tidal elevation (left). Example of tidal compensation for single profile (right).

Usage#

This script is designed to be used from the terminal (i.e. command line).

Command line interface#

The script can handle three different inputs:

  1. single SEG-Y file (e.g., filename.sgy)
  2. datalist of files to process (e.g., datalist.txt)
  3. directory with input files (e.g., /input_dir)

Additionally, the directory path of the tidal constituent netCDF files (provided from OSU) is required (model_dir).

There are two options to run the script. We recommend using the CLI entry point like:

>>> 06_compensate_tide {filename.sgy | datalist.txt | </directory>} [optional parameters]

Alternatively, the script can be executed using the (more verbose) command:

>>> python -m pseudo_3D_interpolation.tide_compensation_segy {filename.sgy | datalist.txt | </directory>} [optional parameters]

Optionally, the following parameters can be specified:

  • --help, -h: Show help.
  • --output_dir {DIR}: Output directory (either --inplace or --output_dir are required!).
  • --inplace: Replace input data without creating copy (either --inplace or --output_dir are required!).
  • --suffix {sgy}: File suffix (default: sgy). Only used if directory is specified.
  • --filename_suffix {SUFFIX}: Filename suffix (e.g. pad, static) to filter input files. Only used if directory is specified.
  • --txt_suffix {despk}: Suffix to append to output filename (default: despk).
  • --constituents, -c: Available tidal constituents supported by TPXO9 atlas model.
    • defaults: M2, S2, K1, O1, N2, P1, K2, Q1,
    • 2N2, K2, M4, MF, MM, MN4, MS4,
    • S1 (only v5)
  • --correct_minor: Correct for minor tidal constituents.
  • --src_coords: Byte position of input coordinates in SEG-Y file(s).
    • source (default)
    • CDP
    • group
  • --crs_src: Source CRS of SEG-Y file(s). Indicate using EPSG code or PROJ.4 string.
  • --write_aux: Write times and tide predictions to auxiliary file (*.tid).
  • --verbose {LEVEL}, -V: Level of output verbosity (default: 0).

Python script#

Additionally, it is possible to just import the essential functions read_parameter_file, tide_predict, and write_tides when using these methods in a custom script:

Import package#

from tpxo_tide_prediction import (
    read_parameter_file,
    tide_predict,
    write_tides
    )

Read input parameter from file#

# (A) read inputs from parameter file
lat, lon, times = read_parameter_file('path/to/parameter/file.txt')

# (B) read only `time` from parameter file and provide fixed location
lat = -36.446349
lon = 175.166068
lat, lon, times = read_parameter_file('path/to/parameter/file', lat, lon)

Compute tidal elevation#

# lat, lon:  int, float, np.ndarray
# times:     str, np.ndarray(dtype='datetime64[s]')

# (A) default configuration
tide = tide_predict('path/to/TPXO9-atlas-model', lat, lon, times)

# (B) custom configuration (less constituents, no correction of minor constituents)
tide = tide_predict('path/to/TPXO9-atlas-model', lat, lon, times,
                    constituents=['m2','s2','n2','k2'], correct_minor=False)

Write computed tides to formatted output file#

# (A) custom output file
# full output (tide at every time at every location)
write_tides('path/to/output/file.tide', tide, mode='full')
# or `track` output (lat-lon-time triplets)
write_tides('path/to/output/file.tide', tide, mode='track')

# (B) create output file from parameter file
basepath, filename = os.path.split('path/to/parameter/file.txt')
basename, suffix = os.path.splitext(filename)
write_tides(basepath, basename, tide, mode='full')

References#

Egbert, Gary D., and Svetlana Y. Erofeeva. "Efficient inverse modeling of barotropic ocean tides." Journal of Atmospheric and Oceanic Technology 19.2 (2002): 183-204.

Last update: Monday, 03 July 2023 at 09:46:51