Tide Stations

Picton Harbours maintains three tide stations in the Marlborough Sounds. Each has a pressure sensor and a radar sensor. Measurements are taken every ten minutes and reported by AIS broadcast and via cellular data to Marlborough’s data distribution platform.

Marlborough managed tide stations are located at:

Motuara Island (-41.093883°, 174.271459°)
Okukari Bay (-41.201612°, 174.311423°)
Te Weka (-41.249400°, 174.192815°)

Port Marlborough maintains a tide station at Waitohe Wharf. It has a radar sensor. Measurements are taken once a minute and reported distributed via NMEA.

Waitohe Wharf (-41.282436°, 174.006476°)

AIS Messages

Stations transmit AIS messages 21 and 8 once every six minutes on each channel, offset by three minutes. Message 21 reports the station name and coordinates. Message 8 reports a composite tide height that considers inputs from both pressure and radar sensors.

NMEA Messages

The sensor types are:

D = Linear Displacement

The units are:

M = Meters

The sensor names are:

HTIDE = Tide Height
SDTID = Tide Height Standard Deviation

Data is available for:

Motuara Island on port 12020
Okukari Bay on port 12021
Te Weka on port 12022
Waitohe Wharf on port 12029

$WIXDR,D,1.148,M,HTIDE,D,0.016,M,SDTID,*6D

JSON Messages

More complete data is available for Marlborough-managed tide stations via JSON messages, available on request. Message format is:

{
  "sensor_id": "pcn.motuara.tidestation.1",
  "timestamp": "2022-03-09T04:20:00Z",
  "measurement_id": "28e01e3b-1a73-9c2e-d16c-29aba7cb9125",
  "tide_height": 0.734,
  "tide_height_sd": 0.022,
  "measurement_type": "pressure_sensor",
  "pressure_measure": 1.871,
  "pressure_measure_sd": 0.022,
  "ais_water_level": null,
  "radar_level": 0.753,
  "radar_level_sd": 0.001538,
  "radar_range": 1.821,
  "radar_status": "0",
  "radar_signal_strength": null,
  "ais_timestamp": null
  }