UXO – unexploded ordnance – is the kind of nasty surprise that can ruin a good day and knowing where bombs are before construction work begins is wise. If your construction site happens to be very close to a fortification and a strategic harbour then an investigation becomes essential.
Last week UWIS & AccuPixel was out in the English Channel working with Apex Diving and Marine, supporting a project to investigate 140 magnetometer targets ahead of the construction of a new pipeline in Newton’s Cove.
Diver Survey
The proximity of Nothe Fort and Portland Harbour put the risks of unexploded ordnance high enough to conduct a full diver survey of every target, gathering evidence of what was found and removing anything nasty.
After deploying the buoys the first dive of the day was to investigate a target before moving tight inshore on a high spring tide. With a tracking up to 500m the inshore work was comfortably in UWIS range (we were working 180m from the furthest buoy) but the very shallow depth of water – less than 2m at high tide – was going to test the kit.
Shallow Water
UWIS tracking software reported the diver’s position close to shore with little difficulty, recording the position of the diver to the log file while giving us visual feedback as the diver excavated the target.
The rugged Panasonic Toughbook gave us a live display of where the diver was at all times, with the master buoy holding the permanent log of the day’s activities – very useful when the need to record and demonstrate all targets were investigated.
As the tide turned the job moved back from the shore and two more boxes were searched with the metal detector. There was no need to relocate the UWIS buoys and with 7hrs of battery once deployed they remained operational throughout the day.
Fishing weights and stainless steel wire were the only finds of the day and with the last target signed off as benign, the buoys were recovered.
Post Dive Analysis
Later the UWIS log was downloaded and imported into Global Mapper with additional map layers added to give the diver tracks context.
Global Mapper is a very versatile tool that can work with many formats of GIS related spatial information making it a very good fit for anyone who requires dive track presentation and analysis.
Summary
The use of UWIS in very shallow water was proved with no requirement to calibrate prior to deployment or to relocate buoy positions during the day. The long battery life and constant logging allowed the divers could concentrate on the work at hand.
The next steps? UWIS can output a NMEA sentence reporting diver position so the goal is to display that on the boat’s navigation equipment.
Watch this space!