The a Irborne Laser Bathymetry T Echn Ique

Hydrographic surveying and nautical charting play a vital role in the safety of navigation in coastal areas, and are thus essential to world maritime commerce. However, the status of hydrographic surveys and nautical charting world-wide is usually quite poor. As a result of the United Nations Convention on the Law of the Sea (UNCLOS), coastal states will be responsible for surveying and charting their Exclusive Economic Zones (EEZ). This is a monumental task for all coastal states, but particularly for those with enormous coastlines, such as Canada with over 200,000 km. The above requirements must be met by technology that can provide nearly 100% bottom coverage and cover large areas quickly. Multibeam swath acoustic systems now provide virtually complete bottom coverage, and are ideal in deeper waters where their swath coverage is large. In shallow coastal waters of less than 50 m, however, even these systems become less cost-effective since their swath width is typically limited to about twice the water depth and they are vulnerable in shoalinfested waters. Moreover, these systems cannot survey up to the land/water interface, and certainly not onto the adjacent land itself. Fortunately a recent technology, Airborne Laser Bathymetry (ALB), has developed into an ideal complement to acoustic swath mapping in shallow coastal waters, and has now been proven to be operationally viable. ALB is analogous to acoustic depth measurement, but uses light instead of sound (Figure 1). As an airborne technique it has several advantages over ship-based systems: