New navigation charts bring economic and maritime safety benefits to Tonga

4 June 2020

Navy disaster relief vessels and other large ships will no longer rely on old fashioned plumb lines and charts measuring in fathoms to enter some of Tonga’s waters, as they have done since the 1800s.

A partnership between Land Information New Zealand (LINZ), the Ministry of Foreign Affairs and Trade, and Pacific governments is coming to fruition with the publication of new electronic navigational charts for the Kingdom of Tonga.

The new charts, created using hydrographic surveys of the undersea world around Tonga, will be vital if large ships are to navigate the reefs and hidden rocks safely. They also ensure compliance with international maritime regulations.

A composite chart of Nomuka Island’s south-west coast showing the original late-1800s chart marked with fathoms (left) and the 2020 electronic nautical chart
A composite chart of Nomuka Island’s south-west coast showing the original late-1800s chart marked with fathoms (left) and the 2020 electronic nautical chart released in 2020. Nomuka is a small island in the southern part of Ha’apai group of islands in the Kingdom of Tonga.

Ms Kelela Tonga, Director of the Marine and Ports Division at Tonga’s Ministry of Infrastructure, says the charts are of great importance for the safety of navigation of all vessels.

“The production of these charts is a milestone for the future of safe shipping within Tongan waters,” she said.

As well as opening up economic benefits for Tonga, the new ENCs will greatly assist New Zealand’s Pacific aid efforts. For the Royal New Zealand Navy (which surveyed Nuku’alofa in 2015 for the project), the ability to assist Pacific Island neighbours in a natural disaster requires significant pre-planning and an up to date knowledge of harbour approaches, port facilities and other potential landing sites.

“Transporting humanitarian aid, personnel and equipment from New Zealand across the expanse of the South West Pacific to the Islands is the easy part,” said Maritime Component Commander, Commodore Mat Williams.

“It is often the last few miles that pose the greatest challenges. To deliver assistance from the sea to those in need means we need complete trust in all the navigational tools at our disposal.

He said getting disaster relief to the right people, at the right time is a key role of the New Zealand Navy in the Pacific. 

“If the worst was to happen, the new ENCs now give us increased confidence in accessing other locations around Tonga for the delivery and distribution of aid.”

In 2019, New Zealand’s High Commissioner to Tonga Her Excellency Ms Tiffany Babington delivered thirty thousand gigabytes of data from the survey work to the Tongan government. The data featured never-before seen images of the sea floor, previously uncharted rocks and reefs along with a number of interesting geological features including a small underwater volcano.

New Zealand, through LINZ, is responsible for the production and maintenance of nautical charts for the Kingdom of Tonga, Niue, Tokelau, Cook Islands and Samoa through the Pacific Regional Navigation Initiative (PRNI), which helps these nations to meet their international maritime obligations.

Water depths around the Tongan islands of Tofua and Kao collected by airborne LiDAR and multi-beam echo sounders show a number of interesting geological features.

Water depths around the Tongan islands of Tofua and Kao collected by airborne LiDAR and multi-beam echo sounders show a number of interesting geological features. To the north, Kao is an active volcano with an intact cone. Canyons exist along the western edge where submarine canyons have formed from significant gravity flows. North of Kao, a young seamount is seen at the water surface. This is a navigational hazard as it is mostly submerged but very shallow at its peak. The peak has been ground flat from wave energy and it harbours rich marine biodiversity.

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