Towards mapping Nereocystis luetkeana kelp beds: using the holonomic iROV SeaBiscuit and sonar fusion

Mapping the density and distribution of kelp beds and assessing change over yearly cycles are important objectives for coastal oceanography. The intelligent, position-aware, holonomic ROV (iROV) SeaBiscuit has been designed specifically for this nearshore 3D mapping application. With the aim of providing high-usability maps on a budget feasible to small-scale field research teams, SeaBiscuit fuses the data from two complementary sonar units and a full navigation suite to explore and map the nearshore environment. Holonomic motion in the horizontal plane and a streamlined profile designed to aid station keeping provide the high degree of manoeuvrability required to operate in this complex environment. The orthogonal arrangement of a forward-facing multibeam sonar and a 360° scanning sonar provide increased coverage and allow 3D maps to be generated in-transit using the holonomic capabilities of the vehicle. Successful field trials saw the mapping of a piling dock before the surveys moved to the kelp beds of British Columbia, Canada. SeaBiscuit was initially calibrated and tested on an 'artificial' kelp bed of kelp stipes transplanted to a sheltered but open-water real world environment. In the summer of 2011, the first successful open ocean kelp bed maps were gathered. It was possible to identify clusters of stipes, to convert this into a useful measure of biomass and to generate a density surface across the kelp bed. Future work to be reported in subsequent papers includes further development of the navigation capabilities of the vehicle and the results of the full-scale kelp bed mapping.