Filter First Order Region (FOR) Based on Amplitude Thresholds

This function filters the First Order Region (FOR) Doppler bins based on amplitude thresholds. It applies a combination of noise-based and peak power-based criteria to remove low-amplitude bins that do not meet the required signal-to-noise ratio.

Usage

seasonder_filterFORAmplitudes(seasonder_cs_object)

Arguments

seasonder_cs_object

A SeaSondeRCS object containing spectral data and FOR parameters.

Value

The updated SeaSondeRCS object with the filtered FOR bins.

Details

Steps in FOR Amplitude Filtering:

1. Retrieve First Order Parameters:

   • The function extracts flim (Null Below Peak Power) and noisefact (Signal-to-Noise Factor) from seasonder_getFOR_parameters.

2. Compute Noise Levels:

   • Calls seasonder_computeNoiseLevel to estimate the average noise level across all range cells.

   • Converts the noise level into a filtering threshold by multiplying it by noisefact.

3. Extract Smoothed Self-Spectra Data:

   • Retrieves the smoothed self-spectra (SSA3) using seasonder_getSeaSondeRCS_FOR_SS_Smoothed.

   • Extracts the FOR spectral power for each range cell using seasonder_extractFOR.

4. Determine Filtering Thresholds:

   • Computes a power threshold for each FOR region by taking the maximum amplitude in the FOR region and dividing it by flim.

5. Apply Filtering Conditions:

   • A Doppler bin is retained if its power is greater than:

     • The noise threshold (computed from noisefact).

     • The power threshold computed from flim.

6. Store Filtered FOR in Object:

   • Updates the SeaSondeRCS object with the filtered FOR bins.

This filtering ensures that only strong, reliable first-order Bragg signals are retained, reducing the impact of noise and second-order contamination.

See also

• seasonder_computeNoiseLevel for computing noise levels.

• seasonder_getSeaSondeRCS_FOR_SS_Smoothed for retrieving smoothed self-spectra.

• seasonder_extractFOR for extracting FOR spectral power.

• seasonder_setSeaSondeRCS_FOR for storing the filtered FOR data.