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 measure, evaluate and study all these subjects, the continuous or at least repetitive monitoring of inshore waters is essential. The new European Water Framework Directive requires regular and repeated monitoring 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 labor input and time. With the intention to provide area-wide surveying of shallow water areas (reservoir beds, river beds, lake beds) 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 laser pulses from the sensor to the objects and back. To capture targets below the water surface, a green laser wavelength has to be selected matching the transmittance window of water. Supplementary information about intensity and waveform of the laser echo pulses are necessary to find a correct interpretation of the recorded signals.