The Fun and Challenges of the DriX Maiden Survey in Tonga

 

From concept to maiden nautical charting survey in just two years is an incredible feat.  And how privileged the iXblue survey team is to not only conduct the maiden survey of the Unmanned Survey Vessel (USV) DriX, but to do so in a region as beautiful as Tonga.

Two years ago, this vessel was merely a concept in the head of Sebastien Grall – the Director of the iXblue shipyard in LaCiotat, France.

Now, the vessel is being used as a primary survey sensor on a multi-million-dollar commercial survey contract.

And I’m so excited about how well this project is progressing, that I’ve prepared this article whilst on board the host vessel, instead of waiting to return to Australia.

The beauty and challenges of the survey region

The Tongan survey area encompasses long and deep corridors between several island groups.  These corridors are characterised with water depths between 30m and 1,000m and consequently are not ideally suited for the DriX which is only fitted with an Em2040C Multibeam echo-sounder.

However, the island groups are characterised by the most amazing seabed morphology that our survey team have ever seen.  Words cannot describe the beauty of the seafloor in this region.

Full seafloor coverage is required around all of the islands and surrounding reefs.  Seafloor depths vary from 5m to several hundred metres in less than 100m in some places.

The challenge for the survey team has been the development of an operational plan which allows both the host vessel (fitted with Em2040C MBES) and the DriX to safely operate in a fast and efficient manner.

Operational constraints include the use of a WIFI system for the control of the DriX with an effective range of only 3 kilometres.  Other constraints include the requirement to launch and recover the DriX in perfectly benign conditions.

Amazing operational efficiency

At the end of our first planned port visit, 6 days were spent in the survey area undertaking MBES activity.  The DriX has been deployed and operational for all of this time, with the exception of a short period to refuel and download the raw survey data.

Since arrival on site, wind and sea conditions have been favourable and have facilitated a trouble-free introduction to this technology.

The team has adopted a slow and steady approach to the use of DriX.  Simple activities such as line planning, switching between autopilot and manual modes and maintaining complete control of the vessel at all times remotely has been both fun and challenging.

One thing that has become clear is that a communication system with a longer range will yield greater efficiency and autonomy.

Very positive results so far

After several days of operating in and around the shallow islands and reefs, it is clear that the DriX is a significantly safer and more efficient option than the 30m host vessel for this type of work.

The DriX has now completed several hundred line miles of shallow water surveying without incident and the team has complete confidence in the vessel.

The Em2040C MBES is being operated in the dual swath mode and with survey speeds between 8 and 9 knots, the sounding density and data quality is better than we have ever achieved.  It must be noted that we have been blessed with favourable wind, sea and sound velocity conditions, but so far the experience has been nothing but positive.

As with any large survey project, it is always best to plan for the worst and hope for the best.  With the experience to date, we remain confident that we are on a winner with the DriX design and look forward to a program of continuous development over the coming months and years.

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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