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Bathymetric Lidar systems operate in a manner that is similar to
their Airborne Lidar Mapping (ALM) counterpart, with one notable
exception. Bathymetric systems transmit two light waves, one in
the infrared and one in the green spectrum, and are capable of detecting
two returns that delineate the water surface and seabed. The infrared
band is quickly absorbed and is therefore used to detect the water
surface, while the green band is used as the optimum color to achieve
maximum penetration in shallow water. Lidar bathymetry systems operate
at a much slower rate, currently around 1000 soundings per second,
due to the need to generate a much longer laser pulse and higher
power requirements.
Bathymetry mapping is a stand-alone Lidar data product.
Despite the high cost of acquiring an ALB system, the methodology
offers significant savings both in operational cost and productivity
increases, when compared to conventional survey methods. ALB mapping
can be conducted in clear water in depths up to 50m. This of course
is a function of water clarity and will decrease with increased
water turbidity. ALB systems are generally flown from fixed or rotary
wing aircraft, due to their size, weight and power requirements.
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