Bias Correction Procedures for Airborne Laser Hydrography

Of the many error sources associated with airborne laser hydrography, one of the potentially most serious is the effect of the scattering of the optical beam into a cone of continually increasing angle, i.e., of underwater light propagation. Depending on the entry nadir angle of the beam and the optical properties of the water, one of two opposing effects -- multiple scattering and geometric "undercutting" — will dominate and result in either a deep or shallow depth measurement bias, respectively. The magnitude of this bias can greatly exceed international hydrographic accuracy standards, and hence bias correctors must be calculated and applied to the raw depths in post-flight data processing to attain the required accuracy for the overall system. The magnitudes of the bias correctors depend not only on the water and flight parameters, but also on the basic design of the receiver electronics. This report describes results obtained for several typical systems* outlines the procedures required to calculate a set of bias correctors for any given system, and includes a cookbook approach for the necessary post-flight data processing algorithms. 1981 OTES (Ocean Technology and Engineering Services) Library Public Domain 1930