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Tonga Eruption Seabed Mapping Project - TESMaP

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Aerial view of HT-HH, showing new multibeam depth data overlaid on a satellite image


In April 2022, NIWA and The Nippon Foundation announced a mission to discover the undersea impacts of the recent Tongan volcanic eruption.

Phase 1 (April/May 2022) saw NIWA scientists survey the ocean around the Hunga-Tonga Hunga-Ha'apai (HT–HH) volcano, covering thousands of square kilometres and collecting video images of the eruption’s impact from the research vessel Tangaroa

Phase 2 (July/August 2022) utilised SEA-KIT's Uncrewed Surface Vessel (USV) Maxlimer to conduct a month of further mapping inside the caldera.



The eruption of the Hunga-Tonga Hunga-Ha'apai (HT–HH) volcano in January 2022 was unprecedented and unexpected, with catastrophic consequences. 


With similar volcanos around the globe, particularly in the Pacific Ring of Fire, the eruption of HT–HH highlights a risk to society from lack of knowledge. Research of this kind is therefore vital to help protect people from similar natural disasters in the future.

Why a USV?

The use of USV Maxlimer as a configurable platform for a range of sensors provided a unique opportunity to safely gather data from inside the caldera for phase 2 of the project. Sensors onboard collected bathymetric data, water column backscatter data, sound velocity, conductivity, temperature, turbidity, oxidation reduction, pressure with depth and currents, all of which will develop and support understanding of the eruption’s undersea impact and ongoing activity.


During the mission USV Maxlimer used less than 2% of the fuel consumption of a typical survey vessel. Deployment of a USV for this survey inside the caldera therefore not only reduced risk to people, but also ensured that the carbon emissions for the project were significantly lower. The unmanned vessel also used innovative winch and sensor deployment capability to collect water column data down to 300m.



Survey area covered inside the caldera of HT-HH


Distance travelled by USV Maxlimer during survey ops

34 days

On operation for phase 2 of the TESMaP project

SEA-KIT USV Maxlimer returning from HT-HH caldera in Tonga

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USV Maxlimer returning from the Hunga-Tonga Hunga-Ha’apai (HT-HH) caldera

USV Maxlimer returned from her initial survey mission inside the caldera of the Hunga-Tonga Hunga-Ha'apai (HT–HH) volcano loaded with astounding data and imagery.


She successfully mapped an area of over 800km² and travelled a distance of 1331 nautical miles during 34 days on operation for TESMaP, controlled remotely from our UK base over 16,000km away. Data and imagery collected by Maxlimer is helping scientists understand how the volcano has changed since its recent eruption. Multiple Conductivity Temp Depth (CTD) and Miniature Autonomous Plume Recorder (MAPR) casts were completed during the mission using the winch whilst the vessel was on the move, also known as 'tow-yos'.


It is the first time that a USV has been used for this type of task and demonstrates how the technology is pioneering new ways of understanding our oceans.

Read NIWA's project round up press release here.

The Tonga Eruption Seabed Mapping Project (TESMaP) was funded by The Nippon Foundation – the largest non-profit organisation based in Japan which, amongst other philanthropic activities, has been facilitating projects in the ocean field since 1962.  The research was also supported by The Nippon Foundation-GEBCO Seabed 2030 Project which aims to map the world’s ocean floor by 2030.

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