Exporting Radial Metrics
In SeaSondeR: Radial Metrics from SeaSonde HF-Radar Data

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  error = TRUE
)

library(SeaSondeR)

Exporting Radial Metrics in SeaSondeR

This vignette demonstrates how to export radial metrics from HF-Radar spectra using the SeaSondeR package. The exported radial metrics table contains key parameters (e.g. DOAs, FOR limits, signal strengths) that can be used with tools such as Sea Display.

Example

# Set sample file paths
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")

# Read the antenna pattern file to create a SeaSondeRAPM object
apm_obj <- seasonder_readSeaSondeRAPMFile(apm_file)

# Create a SeaSondeRCS object from a spectral file
cs_obj <- seasonder_createSeaSondeRCS(cs_file, seasonder_apm_object = apm_obj)

# Compute first-order regions and run the MUSIC algorithm if needed:

cs_obj <- seasonder_computeFORs(cs_obj, FOR_control = list(nsm = 2, fdown = 10^(10/10), flim = 10^(20/10),
                                                            noisefact = 10^(6/10), currmax = 2,
                                                            reject_distant_bragg = TRUE, reject_noise_ionospheric = FALSE,
                                                            reject_noise_ionospheric_threshold = 0))
 cs_obj <- seasonder_runMUSICInFOR(cs_obj)

# Define a land mask (AngSeg) to remove onshore data
AngSeg <- purrr::list_c(lapply(45:61, function(i) list(c(i, 313, 360), c(i, 0, 31))))

temp_file <- tempfile(fileext = ".ruv")

# Export the radial metrics in LLUV format
radial_metrics <- seasonder_exportLLUVRadialMetrics(cs_obj,
                                                    LLUV_path = temp_file,
                                                    AngSeg = AngSeg)

# Display the first few rows of the exported radial metrics
head(radial_metrics)

The example above exports the radial metrics into a file (LLUV format) that can later be reviewed using visualization applications such as Sea Display.

Description of the Radial Metrics Table

Below are the columns of the exported Radial Metrics table in SeaSondeR.

| Column | Description | | -------------------- | -------------------------------------------------------------------------------------------------------- | | LOND, LATD | Longitude and latitude (decimal degrees) | | VELU, VELV | East and north components of velocity (cm/s) | | VFLG | Vector validity (see below) | | RNGE | Distance from the antenna (km) | | BEAR | Bearing of the vector (counter-clockwise from true north) | | VELO | Radial velocity (cm/s) | | HEAD | Velocity direction (counter-clockwise from true north) | | SPRC | Range cell | | SPDC | Doppler bin | | MSEL | Selected solution (1 = single, 2 = dual 1, 3 = dual 2) | | MSA1 | Bearing of the single solution (1440 if invalid) | | MDA1, MDA2 | Bearing of the first and second dual solutions (1440 if invalid) | | MEGR | Ratio of the first and second eigenvalue | | MPKR | Signal power ratio | | MOFR | Off-diagonal ratio | | MP13 | Phase between antennas 1 and 3 | | MP23 | Phase between antennas 2 and 3 | | MSP1 | Signal power of the single solution (dB) | | MDP1, MDP2 | Signal power of the first and second dual solutions (dB) | | MSW1 | 3-dB width of the DOA function below the peak for the single solution | | MDW1, MDW2 | 3-dB width of the DOA function below the peak for the first and second dual solutions | | MSR1 | Value of DOA function at the peak of the single solution | | MDR1 | Value of DOA function at the peak of the first dual solution | | MDR2 | Value of DOA function at the peak of the second dual solution | | MA1S, MA2S, MA3S | SNR of the self-spectrum of antennas 1, 2, and 3 for this Doppler bin | | MEI1, MEI2, MEI3 | First, second, and third eigenvalue of the covariance matrix | | MDRJ | Reason for dual-solution rejection (see below) | | PPFG, PWFG | Flags for QARTOD tests 103 and 104 (1 = pass, 4 = fail) |

VFLG

The value is composed as a sum of powers of 2, representing a binary number where each bit indicates a specific flag.

| Value | Description | | ------- | -------------------------------- | | 0 | Valid vector | | +64 | Low SNR | | +4096 | Either PPFG or PWFG is not equal to 1 |

MDRJ

This value is also composed as a sum of powers of 2, where each bit represents a flag.

| Value | Description | | ------- | ----------------------------------------------------------------------------------- | | 0 | Dual solution not rejected | | +1 | P1 test failure | | +2 | P2 test failure | | +4 | P3 test failure | | +8 | The angle difference between both solutions is less than 20 degrees | | +16 | Only one peak was found in the dual solution |