Lidar surveying uses airborne lasers to map the seafloor. A low-flying aircraft scans pulsed laser beams across the seafloor to generate a swathe of depth soundings. For example, the Laser Airborne Depth Sounder (LADS) uses a scanning mirror that reflects a green laser back and forth across the flight path in a grid pattern. The laser penetrates the water column to a limit of about 50-70 m (in clear water). The LADS flight unit is based in Cairns, Australia and is operated by the Royal Australian Navy. These images were taken during a LADS survey over dense coral reefs in the northern Great Barrier Reef.