Lidar (light detection and ranging) technology measures elevation or depth by analyzing the reflection of pulses of laser light off an object. Lidar survey systems are typically aircraft mounted and provide seamless, contiguous coverage between land and sea.
Bathymetric lidar is used to determine water depth by measuring the time delay between the transmission of a pulse and its return signal. Systems use laser pulses received at two frequencies: a lower frequency infrared pulse is reflected off the sea surface, while a higher frequency green laser penetrates through the water column and reflects off the bottom. Analyses of these two distinct pulses are used to establish water depths and shoreline elevations. With good water clarity, these systems can reach depths of 50 meters.
Bathymetric lidar is also used to acquire data in areas with complex and rugged shorelines where surface vessels cannot operate efficiently or safely because of rocks, kelp or breaking surf. Some examples of these areas include Alaska, the North Atlantic Coast and the Caribbean.