FU Classification - Algorithm Specification

Introduction

This algorithm is used for deriving the hue angle and FU (Forel-Ule) value from remote sensing reflectance. The data is used with the weighted linear sum of the remote sensing reflectance in which visual bands plus a correction term for the specific band-setting of each instrument. The algorithm is validated by a set of 603 hyperspectral measurements from inland, coastal and near-ocean waters. The processor supports the the following sensors:

The algorithm is described in the following articles which are available online.

Extending the derivation of the hue angle to more instruments.
Van der Woerd, H.J., Wernand, M.R, 2018. Hue-Angle Product for Low to Medium Spatial Resolution Optical Satellite Sensors (http://dx.doi.org/10.3390/rs10020180)
The derivation of the hue angle for the instruments SeaWiFS, MODIS, MERIS and OLCI are described in:
Van der Woerd, H.J., Wernand, M.R., 2015. True colour classification of natural waters with medium-spectral resolution satellites: SeaWiFS, MODIS, MERIS and OLCI. Sensors 15, 25663-25680. doi: 10.3339/s151025663 (Open Access)
The conversion of the hue angle to the Forel-Ule number and the corresponding colour legend is based on:
Novoa, S., Wernand, M.R, Van der Woerd, H.J., 2013. The Forel-Ule scale revisited spectrally: preparation protocols, transmission measurements and chromaticity. JEOS RP 8, 13057. DOI: http://dx.doi.org/10.2971/jeos.2013.13057 (Open Access)
This algorithm connects satellite ocean colour observations to historical in-situ colour observations:
Wernand, M.R, Van der Woerd, H.J., Gieskes. W.W.C, 2013. Trends in ocean colour and chlorophyll concentration from 1889 to present. Plos One. http://dx.plos.org/10.1371/journal.pone0063766 (Open Access)