Airborne Hydromapping - Area-wide Surveying of Shallow Water Areas

Reservoir sedimentation and river degradation, water flow and water level dynamics, structure and zone variations of rivers and riparian areas - in order to gage, to state and to research, the continuously or at least repetitively monitoring of our inshore waters is essential. The new European Water Framework Directive determines the regular, repeated monitoring as a fixed constant for surveillance, operation, investigation and reference. Hydrographic profile measurements are the basis for every close to reality study and task. Conventional methods like mechanical or sonic systems require major labour input and time. With the intention to provide an area-wide surveying of shallow water areas (reservoir beds, river beds, lake beds) the technique of laser ranging and LIDAR (Light Detection And Ranging) has been adopted and is further explored to extend its capabilities to shallow waters. The distance to an object is determined by measuring the time of flight of the laser pulses from the sensor to the objects and back. To capture things below the water surface a green laser wavelength has to be selected matching the transmittance window of water. Supplementing information about intensity and the modifications in waveform of the laser echo pulses are necessary to interpret the recorded signals.