The world’s first ever survey project (of scale) using Satellite Derived Bathymetry (SDB), Airborne Bathymetric Lidar (ABL) and a vessel mounted multi beam echo sounder was successfully completed in Tonga on Christmas Eve.
The challenges were many, including the scale of the project, shallow waters in places, some unchartered waters and old data and charts for reference.
Our part of the project - Stage 3 - was made a lot easier and safer due to the work carried out in Stages 1 and 2.
Stage 1 – One of the largest SDB surveys ever undertaken
The Land Information New Zealand (LINZ) project commenced in early 2018, with EOMAP completing one of the largest area, Satellite Derived Bathymetry survey projects ever undertaken by any company in the world.
It covered an area in excess of 1,500 km2 across the Tongan region. The SDB component of the survey allowed LINZ to accurately position all of the islands across the survey area in a very cost-effective manner.
The SDB data also allowed for more robust planning of the ALB campaign by identifying shallow water areas of interest that would have otherwise been missed.
Stage 2 – ALB survey with 400% increase in density
In mid-2018, US based ALB experts, Geomatics Data Solutions (GDS) completed a survey over many of the low-lying reefs and atolls that are routinely used my mariners in the Tongan region.
The ALB survey utilised a newly released enhancement to the Leica Chiroptera, which allows the system to survey at four times the sounding density than was previously possible. The ALB system was used to survey all of the area to depths up to 20m to the IHO Order 1a standard.
This proved to save considerable time for our vessels undertaking the multibeam component of the survey in stage 3. With the shallow waters surveyed in entirety prior to arrival, the vessels were free to safely navigate the region day and night at any speed without fear of grounding on an unchartered feature or poorly charted reef.
Stage 3 – ground breaking unmanned survey vessel survey
In early November, after the one-week transit from New Zealand, the 30m mothership – MV SILENT WINGS and the new iXblue 8m unmanned survey vessel DriX, were on site and ready to survey what was estimated to be a 4,580nm survey.
Being so close to Christmas, it was going to be touch and go whether the survey and vessel crews would be finished in time to be home for Christmas. There was little time in the schedule for vessel or equipment failure and certainly no time for a cyclone or extreme weather event.
Over the course of the next 42 days, the vessel crew, survey crew and both vessels worked around the clock to progress the survey.
- Several port visits were made to Nukualofa for fuel, fresh food and crew rotations.
- Numerous uncharted seamounts and volcanoes were surveyed throughout the period and with it, a dataset that contains some of the most spectacular seabed morphology ever surveyed by iXblue.
- In the early hours of Christmas eve, the survey team ended the last line for the survey. A total of 5,308nm had been surveyed in just six weeks.
- The weather had been mostly kind, the survey vessels and survey systems highly reliable.
- All tide gauges were successfully recovered with no loss of data.
Most importantly, the survey was completed with no injuries or incidents. The DriX had proved its worth early on and has cemented its place as a valuable tool in the iXblue survey inventory. We are very much looking forward to getting it in the water again for the next survey.
The final stage
The iXblue survey team now has the challenging task of completing the data processing and compiling the final report for LINZ. This will be progressed over the coming months.
A big thank you to all of the team and vessel crew who worked closely together to make this project such a success. It is a credit to your expertise and professionalism that this project was completed to such a high standard.