Fiordland bathymetric survey

After weeks of soaking up spectacular scenery and battling challenging weather and midges, we left the magnificent Fiordland National Park region in the south-west corner of New Zealand’s South Island.  It was April 2019, and we had just completed another survey for Land Information New Zealand Annual Survey (LINZ).

Why Fiordland needed to be surveyed

The Fiordland National Park is characterised by some of the most spectacular fiord systems in the southern hemisphere.  The breathtakingly beautiful region has become increasingly popular as a tourist destination (17% growth year on year) for local and international tourists who access it via tour vessel operator or chartered aircraft.

At some point during the past few decades, a hydrographic survey of the region was undertaken, but not using technology that imaged the seafloor.  The risk of vessel grounding and an environmental disaster is real, when there is little confidence that every rock and sub-surface feature has been charted.

Only complete coverage of the area using high resolution sonar would enable the creation of up to date, highly accurate charts, to keep all mariners operating in the region well clear of all navigational dangers.

Unique array of equipment we used to survey Fiordland

In a first for iXblue – we used four different vessels, each fitted with high resolution Multi-beam Echosounders, to conduct this survey.  We partnered with Discovery Marine Limited (DML) and mobilised the vessels into the area in January 2019.

As the survey area was subject to a wide variety of environmental conditions, we needed to deploy the right resource and equipment for each region.

  • The challenging wind and sea conditions of the outer regions could only be safely surveyed by the 30m Survey Vessel – SILENT WINGS.
  • The inner regions, characterised by shallow, rocky and a navigationally constrained coastline required a smaller and more manoeuvrable vessel. This is where we deployed the 16m KAREN D catamaran and the iXblue DriX Unmanned Survey Vessel.
  • In the very shallow areas the DML owned 7m Stabicraft was relied upon.

Three Kongsberg Em2040C Multibeam systems and one Teledyne T20 Multibeam system were installed alongside iXblue PHINS Class Inertial Navigation Systems (INS).  Despite operating extensively in steep sided fiords with significant satellite masking, the combination of high-grade INS and the Fugro MarineStar GNSS positioning service resulted in highly accurate and reliable positioning for the full duration of the project.

Rainfall caused havoc

The Southern Fiords receive in excess of 8m of rainfall every year, making it one of the wettest regions of New Zealand, and a very different environment for our survey team to operate in.  In fact, mid-way through the project, the crew received over 500mm of rainfall in just one day!

The extraordinary rainfall creates a significant fresh water layer which wreaks havoc on the beam forming and data quality of the Multibeam echo sounders.  The crew had to ensure that sufficient Sound Velocity profiles were recorded both spatially and temporally.  Valeport MiniSVS, RAPIDPro SVP and SWIFT SVP sensors were used to obtain accurate and reliable Sound Velocity measurements.

The only upside of the heavy rainfall was it stopped the notorious midges from attacking our crew.

iXblue survey crew in Fiordland

Our crew rugged up to ward off the cold wind and the midges

The next phase of the Fiordland project

The “fieldwork” phase of the Fiordland survey involved laser scanning of hundreds of kilometres of rugged coastline with the MERLIN mobile laser scanner, along with over 2,880nm of MBES survey from all four vessels.  Once it was complete, the vessels returned to their home port in Tauranga, New Zealand.

The survey team has now commenced the very different task of cleaning and checking the tidal and bathymetric survey data and compiling the Report of Survey.  This will take hundreds of hours of expert attention over the coming months and will be the final step in what has been a very successful and rewarding survey project.

It was a pleasure to share the experience with the expert team from DML and it was both a pleasure and a privilege to operate in this magnificent corner of the world.

The best outcome of all is that the combined efforts of participants - LINZ, DML, iXblue, Pacific7 and Environment Southland - will result in better navigational and environmental safety for mariners in this beautiful region, for many, many years to come.

David Donohue

As Managing Director David's role is to ensure clients' surveys are undertaken with precision and to meet budgets, schedules and relevant survey standards. His particular driving passion is innovation and process improvement.

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