Tide Stations
- Jonathan Brewer
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,*6DJSON 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
}