LiDAR Bathymetry for Nautical Charting

Safety Of Life at Sea (SOLAS) is the overarching principle for all offshore operations and one of the major contributing factors to SOLAS is quality navigational charts that are comprehensive and adhere to International Hydrographic Organisation (IHO) established standards of accuracy. However, a chart is only as good as the data that is used to compile it and one of the more challenging areas for hydrographic surveyors is the coastal/shallow areas where it can be very time consuming, difficult and sometimes impossible to obtain data using traditional acoustic techniques. The main weapon in the hydrographer’s toolbox is the sonar, whether it is a multibeam, singlebeam or sidescan. Even with these tools we cannot always get data in the shoalest area due to a variety of factors including the vessel’s draught, dangerous terrain etc. Advancement and development in laser technology, electronics and computing systems over the past few decades has resulted in development of systems capable of conducting bathymetric surveys using platforms other than traditional boats/ ships. Airborne Laser (or LiDAR) Bathymetry (ALB) is a technique for measuring the depths of relatively shallow, coastal waters using a scanning, pulsed laser beam operated from an aircraft. It is also known as Airborne LiDAR Hydrography (ALH) when used primarily for nautical charting. It not only provides the capability to survey faster but also enables the hydrographer to reach dangerous areas inaccessible by boat. Though not considered a replacement for acoustic surveys, ALB can be used in conjunction with traditional acoustic surveys for better area coverage and charting the unreachable areas. The paper discusses LiDAR bathymetry concept, its advantages and limitations, operational methodologies, meeting the accuracy challenges with reference to a combined acoustic and LiDAR survey that IIC Technologies has recently undertaken.