Explain Hourly Averaging Process
explain_hourly_averaging.RdEducational function explaining how raw measurements become hourly values.
Examples
cat(explain_hourly_averaging())
#>
#> HOURLY DATA: FROM RAW MEASUREMENTS TO REPORTED VALUES
#> =====================================================
#>
#> RAW DATA COLLECTION
#> -------------------
#> The buoy continuously measures:
#> - Sea surface elevation (heave sensor)
#> - Accelerometers for motion
#> - Other sensors (wind, pressure, temperature)
#>
#> BURST SAMPLING
#> --------------
#> Waves are measured in 'bursts':
#> - Duration: 17.5 minutes (Irish Weather Buoy Network)
#> - Sample rate: Typically 1-2 Hz (1-2 samples per second)
#> - Raw samples per burst: ~1000-2000 measurements
#>
#> SPECTRAL PROCESSING
#> -------------------
#> For each burst:
#> 1. Apply FFT (Fast Fourier Transform) to heave signal
#> 2. Calculate wave energy spectrum S(f)
#> 3. Compute spectral moments: m0, m1, m2, m4
#> 4. Derive parameters:
#> - Hs = 4 * sqrt(m0)
#> - Tp = period at spectral peak
#> - Tz = sqrt(m0/m2)
#>
#> HMAX DETERMINATION
#> ------------------
#> Maximum wave height (Hmax) is determined by:
#> 1. Zero-crossing analysis of the time series
#> 2. Identifying individual waves (trough to trough)
#> 3. Recording the maximum crest-to-trough height
#>
#> HOURLY REPORTING
#> ----------------
#> The ERDDAP data provides ONE value per hour:
#> - This is typically the most recent burst analysis
#> - NOT an average of multiple bursts
#> - Represents conditions at that hour
#>
#> DATA TIMELINE
#> -------------
#> Example for 12:00 UTC value:
#> - Burst collected: ~11:40-11:57 UTC
#> - Processing: ~1-2 minutes
#> - Reported as: 12:00 UTC timestamp
#>
#> QUALITY CONTROL
#> ---------------
#> Each reported value includes a QC flag:
#> - 1 = Good quality
#> - 2 = Suspect
#> - 3-9 = Various quality issues (see Marine Institute documentation)