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G. Mandlburger, M. Pfennigbauer, A. Haring:
"Interaction of laser pulses with the water surface at different wavelengths and angles of incidence";
Talk: CapturingReality: 3D, laser scannning & LiDAR technologies forum, Salzburg; 2015-11-23 - 2015-11-25.

Precise mapping of water surface level heights is not only a prerequisite in airborne laser bathymetry but is also inevitable for other applications in hydrology and hydraulic engineering (flood hazard mapping, habitat modelling, etc.). The interaction of the laser pulse with the water surface is complex and the received return energy depends on many factors like (i) the laser wavelength, (ii) the incidence angle between the laser beam and the water surface, (iii) the sensor-to-target distance, (iv) the laser footprint size, (v) the roughness of the water surface within the laser footprint, and (vi) the water clarity.

In our contribution the nature of laser echo returns from the water surface is empirically investigated. To this end airborne laser scanners operating at wavelengths of 532nm, 1064nm, and 1550 nm are employed to survey different water bodies (sea, large stream, river, and lakes) from varying altitudes. Flying heights range from 25-60m for UAV-based platforms to 600-800m for airborne acquisition. Different angles of incidence result either "naturally" from the scan mechanism or, if this does not apply, are realized through extreme nick angles during flights carried out especially for the purpose of this research. It shows that the angle of incidence and water surface conditions have a much stronger effect on the return signal then the laser wavelength.