{
  "tool": "Harbor Draft Calculator v2",
  "author": "Bryan Takahashi",
  "location": "Raritan Bay, New Jersey",
  "version": "2.0",
  "changeLog": {
    "v2": "Added wave-induced draft variation (±0.5% LOA) per Jimmie Williams' field observation"
  },
  "constants": {
    "noaa_station_id": "8518750",
    "noaa_station_name": "Sandy Hook, NJ",
    "wave_variation_coefficient": 0.005,
    "wave_variation_description": "Fraction of Length Overall representing ±draft variation due to heave/pitch in moderate coastal conditions",
    "minimum_safe_margin_ft": 2.0,
    "caution_threshold_ft": 0.5
  },
  "formulas": {
    "effective_draft_still_water": "draft_keel",
    "wave_induced_variation": "LOA × wave_variation_coefficient",
    "maximum_instantaneous_draft": "effective_draft + wave_induced_variation",
    "available_water_column": "tide_height + charted_channel_depth",
    "safety_margin": "available_water_column - maximum_instantaneous_draft"
  },
  "assessment_rules": {
    "safe": "safety_margin >= minimum_safe_margin_ft",
    "caution": "safety_margin >= caution_threshold_ft AND safety_margin < minimum_safe_margin_ft",
    "unsafe": "safety_margin < caution_threshold_ft"
  },
  "sources": [
    {
      "name": "NOAA Station 8518750",
      "url": "https://tidesandcurrents.noaa.gov/stationhome.html?id=8518750",
      "type": "tidal_data"
    },
    {
      "name": "Naval Architectural Practice: Wave-Induced Vessel Motion",
      "note": "Standard ±0.5% LOA approximation for coastal passage planning"
    }
  ],
  "worked_example": {
    "inputs": {
      "tide_height_ft": 4.2,
      "channel_depth_ft": 12.0,
      "keel_draft_ft": 4.5,
      "loa_ft": 36.0
    },
    "outputs": {
      "effective_draft_ft": 4.5,
      "wave_variation_ft": 0.18,
      "max_draft_ft": 4.68,
      "available_water_ft": 16.2,
      "safety_margin_ft": 11.52,
      "assessment": "SAFE"
    }
  }
}