Depth Measurement Bias in Pulsed Airborne Laser Hydrography Induced by Chromatic Dispersion

In contrast to topographic laser scanning, hydrography must take into account the presence of two media. A pulsed beam, which enters water from air at an oblique angle, is refracted air-water boundary in direction plumb line. This change described by Snellius' law caused a slower speed light wave water, i.e., phase velocity. Light scattering turbidity gives rise further deviations straight path. Together, and turbidity-induced path extension cause longer pulse round trip time than air. For accurate measurement, it important correct this propagation extension. It common practice assume velocity as for pulses water. dispersive medium, however, only approximation pulse. media with chromatic dispersion, propagate different velocity, group using instead reduces range dependent bias depth measurement wavelength 532 nm more 1.5%. We present easy perform experiment, shows that differs so much difference should be taken account. discuss use explain examples literature.