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Perform Doppler Interpolation for SeaSonde Cross-Spectra Data

Source: R/SeaSondeRCS_MUSIC.R
seasonder_SeaSondeRCSMUSICInterpolateDoppler.Rd

This function performs Doppler interpolation on the cross-spectra data of a SeaSondeRCS object, preparing the data for MUSIC processing. Interpolation is achieved by inserting additional Doppler bins using linear interpolation, potentially increasing the number of detected vectors while possibly smoothing the radials. The function tries to mimic CODAR's AnalyzeSpectra tool interpolation, including the addition of a wraparound Doppler cell before interpolation.

Usage

seasonder_SeaSondeRCSMUSICInterpolateDoppler(seasonder_cs_object)

Arguments

seasonder_cs_object

A SeaSondeRCS object containing cross-spectra data and metadata for processing.

Value

A SeaSondeRCS object with updated interpolated cross-spectra data and metadata.

Details

Doppler interpolation increases the number of Doppler bins by a factor of 2, 3, or 4 before radial processing. This is accomplished by linearly interpolating between existing bins, increasing the number of radial vectors by approximately 15% for a 2x interpolation, and yielding smoother radials. The interpolation factor is configurable via the SeaSondeRCS object's doppler_interpolation attribute and it's setter seasonder_setSeaSondeRCS_MUSIC_doppler_interpolation. The number of Doppler bins after interpolation should not exceed 2048; exceeding this limit will result in an error.

The interpolation process is as follows:

  1. A wraparound Doppler cell is added to the right of the data.

  2. For non-quality-control (QC) matrices, linear interpolation is applied to fill in the newly added Doppler bins.

  3. QC matrices are updated with a default value (-1) for interpolated bins.

Note

  • CODAR's SeaSonde R8 Radial Config Setup documentation advises against using 3x or 4x interpolation.

  • The function ensures the number of Doppler bins after interpolation does not exceed 2048.

  • Doppler interpolation is a preprocessing step typically performed by CODAR's AnalyzeSpectra tool before MUSIC processing.

See also

seasonder_setSeaSondeRCS_MUSIC_interpolated_data for setting interpolated data, seasonder_getSeaSondeRCS_MUSIC_doppler_interpolation for retrieving the interpolation factor, seasonder_setSeaSondeRCS_MUSIC_doppler_interpolation for setting the interpolation factor, seasonder_initCSDataStructure for initializing the interpolated data structure.

Examples

# Doppler interpolation
# Create a SeaSondeRCS object for interpolation example
cs_file <- system.file("css_data/CSS_TORA_24_04_04_0700.cs", package = "SeaSondeR")
apm_file <- system.file("css_data/MeasPattern.txt", package = "SeaSondeR")
apm_obj <- seasonder_readSeaSondeRAPMFile(apm_file)
#> seasonder_createSeaSondeRAPM:  APM object created successfully.
cs_obj <- seasonder_createSeaSondeRCS(cs_file, seasonder_apm_object = apm_obj)
#> new_SeaSondeRCS:  SeaSondeRCS object created successfully.
# Perform Doppler interpolation
out <- seasonder_SeaSondeRCSMUSICInterpolateDoppler(cs_obj)