Arrival estimation

Last updated: 19 August 2021

How arrival estimation is reflected in the app

Arrival port and time are estimated for vessels that have entered the region 400 nm off the coast of New Zealand and that have not yet arrived at a New Zealand port. The estimated arrival port and time are displayed in the ‘Track history summary’ section of the vessel details panel, alongside how they have been estimated (source). Arrival estimations can also be found in the ‘Next port’ column of the vessel list.

How arrival estimation works

The estimated arrival port is determined using information from three sources (where available) with the following priority. See table 1 for the list of first arrival ports 1.

Source Estimation priority Description
Port schedule High From a first arrivals port indicating a vessel arriving within seven days
AIS data Medium Self-reported destination sourced from the Automatic Identification System (AIS). Included where available and when it matches a New Zealand first arrivals port
Vessel movements Low Based on vessel velocity and shortest path to a first arrivals port. The shortest path is calculated using Dijkstra’s algorithm and a node network that covers water access routes.

The estimated arrival time window

An arrival window is calculated with a 70% confidence of the vessel arriving within the window. For example, if a vessel is estimated to arrive in 24 hours the arrival window will show the vessel is due to arrive sometime in the next 18–30 hours.

As the arrival time nears the size of the arrival window is narrowed. For example, if a vessel is estimated to arrive in the next 4 hours the arrival window will show the vessel due to arrive sometime in the next 3–6 hours.

Considerations on reliability

  • Port schedules are used when approval has been granted by a port manager. These schedules however are only an indication of the intention of a vessel to arrive and their accuracy is not guaranteed.
  • AIS reported destination is voluntary and self-reported therefore it is not provided by most vessels.

Table 1. List of first arrival ports used in estimation

Region Ports
Northland Opua Marine Park
Marsden Cove Marina
Northport (Marsden Point Cargo Terminal)
Marsden Point Oil Refinery
Auckland Bledisloe and Fergusson Terminals (freight)
Princes and Queens Wharf (passenger)
Chelsea Port, Birkenhead
Devonport (Royal New Zealand Naval Base)
Kauri Point, Birkenhead, (Royal New Zealand Navy)
Viaduct Marina
Silo Marina
Westhaven Marina
Tauranga Port of Tauranga
Vessel Works Marine Precinct
Waikato (Taharoa) Taharoa offshore buoy
Gisborne Eastland Port
Napier Napier Port
New Plymouth Port Taranaki
Wellington Wellington Harbour
Picton Picton Harbour
Nelson Port Nelson
Christchurch (Lyttelton) Lyttelton Harbour
Timaru Timaru Port
Dunedin (Port Chalmers) Port Chalmers
Invercargill (Bluff and Tiwai Point) Tiwai Point
South Port, Bluff
  1. Ministry for Primary Industries. Places of first arrival – seaports. 2020; (12 September). Accessed 17 August 2021.