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Chatham Islands

Client:

Land Information New Zealand

Duration:

5 Months

Budget:

NZ$2.5m

Project Date:

2010/11

Background

In late 2010 iXblue Australia undertook a survey of the Chatham Islands for Land Information New Zealand (LINZ). The Chatham Islands are a rugged, remote island group that lie 250nm east of Christchurch.  The waters in and around the Chatham Islands were poorly charted and accordingly were identified as a priority area for safety of navigation and charting action.

Requirement

LINZ specified a survey with a combination of LINZ MB Order-1 and SB Order-1.  The survey areas included the major anchorage areas, shipping routes and port facilities used by the fishing and tourist industries throughout the Islands. The survey was to be completed and delivered by mid 2011.

Challenges

This survey provided a number of operational and logistical challenges.  The most significant challenges were the extreme weather conditions and the remoteness of the Island group from the NZ mainland.  This was compounded by a requirement to undertake several coastal, shallow water surveys using full coverage multi-beam echo sounders, and several thousand line miles of survey in open, exposed waters.  The size and type of vessels suited for shallow water surveys and for the offshore survey component are quite different.

Survey Solution

To ensure we provided LINZ with the best possible outcomes, we decided to use two vessels fitted with identical survey systems.

  • The  ‘TRANQUIL IMAGE’, (owned and operated by Western Work Boats Ltd) was contracted to undertake most of the offshore survey work.  
  • A smaller, custom built hydrographic survey vessel fitted with a multibeam echo sounder ‘moonpool’ was contracted for the safe survey of the shallow water, navigationally dangerous areas of the project.  
  • Our Kongsberg EM3002D MBES, integrated with an iXblue ROVINS and WADGPS were fitted to each vessel. The system proved its worth during the survey, comfortably handling the weather and rugged nature of the area whilst maintaining a MBES swath width of at least 6 x water depth over much of the area surveyed. 
  • The long period swell risk of the project was eliminated by the use of the iXblue ROVINS ‘Smart Heave’, which effectively removed all heave artefacts from the final dataset.

  • Employing two dual head MBES systems ensured a high rate of data acquisition was obtained during the short weather windows that characterise the survey area.

The survey data was processed using the CARIS HIPS and Bathy Database Suite of hydrographic software, providing our client with quality controlled deliverables.  At the completion of fieldwork, approximately 3,900 line miles (nm) was surveyed in accordance with the contracted specifications.

Early Completion

We were pleased that we actually completed the contracted survey areas several weeks ahead of schedule, giving us the opportunity to survey additional areas and undertake some ‘disproving’ searches that were of interest to LINZ.

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