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Pacific Regional Navigation Initiative – Tonga

Client:

Land Information New Zealand

Duration:

18 months

Budget:

NZD$2m

Project Date:

2017/18

Background

iXblue was awarded a unique and interesting survey project by Land Information New Zealand In late 2017.  The project was one of several components of a larger aid program being funded by the New Zealand Government’s Ministry of Foreign Affairs and Trade.  The Pacific Regional Navigation Initiative was a 5 year, NZD$7.2M dollar program designed to increase the navigational safety of mariners operating in and around the pristine waters of the South West Pacific.

Requirement

With such a large area in need of modern survey and charting, and a budget large enough to cover a fraction of the area required, LINZ had to devise a survey solution that would deliver maximum ‘bang for buck’.

In what is thought to be a world first, LINZ adopted a highly innovative and ambitious plan to incorporate the use of three very different sensor types into the one project.  Accordingly, iXblue was contracted to incorporate Satellite Derived Bathymetry (SDB) and Airborne Lidar Bathymetry (ALB) into the survey solution – in addition to the traditional vessel mounted Multi-beam.

Challenges

The survey area is characterised by hundreds of atolls, reefs and coral outcrops and is one of the most spectacular and interesting seabeds one could ever hope to survey.  The Pacific waters in this part of the world are crystal clear with excellent visibility, and accordingly is the perfect environment for using optical survey sensors such as SDB and ALB.

Attempting to survey these waters just by vessel would have proven to be hazardous, as it was poorly charted and strewn with shallow-water reefs and features.  The plan to survey with SDB and ALB to identify and chart all the shallow water features prior to the vessel entering the area, so the vessel crew could operate 24/7 basis in complete safety.

Survey Solution

SDB Survey – The SDB component was undertaken by EOMAP – a world leader in the delivery of Satellite Derived Bathymetry.  Over a 6-month period EOMAP used a combination of archive and new fly satellite imagery data to compile a dataset that covered many thousands of square miles over Tonga, Niue the Cook Islands and Tokelau.  This data enabled LINZ to accurately position all the islands and drying shoals, reefs and atolls; and in most cases to chart the depths of these and surrounding waters.

ALB Survey.  The ALB component was undertaken by US-based firm – Geomatics Data Solutions Inc.  (GDS). The many uncharted features identified during the SDB survey information enabled the ALB plan to be modified to achiee maximum value.

The ALB survey was undertaken using the latest generation of the Leica Chiroptera ALB system – the 4X version.  This new system generates four times the sounding density of the previous system and delivered unprecedented levels of resolution and seabed detail.  The exceptionally clear water allowed depth penetration in excess of 30m and with it – significant navigational safety to the survey vessel.

MBE Survey.  iXblue undertook the final component of the survey using two vessels fitted with near identical survey systems.

The 30m mothership the MV SILENT WINGS, chartered from NZ-based firm Pacific7 Ltd, was modified to accommodate the new iXblue DriX Unmanned Survey Vessel.  At 8m long and 80cm wide, DriX has been specially designed as a force multiplier, and this was its’ first commercial hydrographic survey.  Both vessels were fitted with Kongsberg Em2040C Multibeam echosounders, iXblue Inertial Navigation Systems, Valeport Sound velocity sensors and multi-channel GNSS receivers incorporating the Fugro MarineStar G2+ correction signal.

Tides and Geodetics.  A four-week tides and geodetics phase was undertaken across the Tonga region between the ALB survey and the Multi-beam survey.  Sailing yacht MY JOCARA was chartered for this phase as a support and accommodation vessel for the survey crew, whilst they deployed and calibrated numerous tide gauges across the survey area, and installed several benchmarks at key locations.

Outcome

Although our survey area only covered a small fraction of the Tongan region, the seabed that was surveyed revealed some of the most amazing features and geomorphology that one could ever hope to see.

The survey field work commenced with the arrival of the ALB aircraft in early July, 2018 and completed with the departure of the SILENT WINGS on Christmas Eve, 2018.

  • The ALB aircraft completed 17 days of flying.
  • The SILENT WINGS and DriX was on site between 8th November and 24th Between them, they had surveyed 7,500km.
  • Numerous uncharted features were detected and will be visible on the updated charts that LINZ will release for use.
  • The dataset collected will be used to improve the navigational safety of mariners who need safe passage through these water ways.
  • The high-resolution seafloor imagery reveals much about the marine habitat and the biodiversity of the flora and fauna that inhabit these waters. It is hoped that the dataset will be of significant benefit to the marine scientists and government agencies with an interest in the coastal zone and marine habitat.

Like many other recent projects undertaken by iXblue, this project was a great privilege and a pleasure to undertake.  Our survey personnel thoroughly enjoyed the challenge of working with the expert personnel from EOMAP and GDS, and the opportunity to combine datasets from other sensor types to deliver one seamless dataset to LINZ.  This, and the combination of six straight weeks of warm, tropical weather, calm seas, fresh fish and regular swims in the Pacific Ocean, made it a survey that will be remembered for a long time.

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