Error propagation at inversion of irradiance reflectance spectra in case-2 waters

Abstract

Many algorithms for determination of water constituents in case-2 waters make use of the Gordon approximation for the subsurface irradiance reflectance. It parameterises the water constituents by specific absorption and backscattering spectra. Based on specific optical properties of water constitutents from Lake Constance, error propagation at inversion of the Gordon algorithm was investigated for concentration values typical for that lake. The following error sources were considered: proportionality factor f in the Gordon equation; curve forms of suspended matter backscattering spectra, Gelbstoff and phytoplankton absorption spectra; concentrations of phytoplankton, suspended matter and Gelbstoff; statistical noise; radiometric resolution. A ranking of the error sources is performed, required accuracies of model inputs are derived, and a strategy for finding suitable start values of the fit parameters is suggested.