A crucial element in the season’s work is the remote sensing process. The aim is to have capability for acquiring, processing, analysing and interpreting good data, with the result of allowing diver based searches of these targets the following day.
Acquiring the data is obtained with a seaborne magnetometer. This device measures distortions in the natural earth’s magnetic field through the presence of iron (or ferrous) material on or under the seabed. The magnetometer is towed on a cable behind the survey vessel, sending readings up the cable to a tablet, which logs the data and provides positioning through a GPS.
The tablet also helps the skipper to navigate along per-positioned lines called transects. These lines have been carefully arranged in mapping software to be straight, and parallel. Narrow line spacing is required to allow sufficient coverage.
Once the data is brought back ashore, it is reviewed on laptops with specialised software. This processs allows for the earth’s magnetic field to be displayed and any distortions detected. Interpretation happens next, with a sifting of potential sites from naturally occurring anomalies.
A list of potential sites is produced, and the most promising analysed more closely. Mapping software allows for the precise positioning for the deployment of divers. Circular shapes are created and placed within the mapping software, which gives a very accurate indication of depths, and can thus inform the dive plan. In this case planning for circular dive searches.
This positioning information is then fed into the tablet, enabling precise navigation to each target.
The entire work flow, carried out by Alex Moss and James Parkinson enables the team to react to information gathered in the field, a sort of ‘reflexive methodology’.