Remote Sensing in the Cloud – Evaluating water optical properties using HICO IPS

This is part of an ongoing series dedicated to reviewing the algorithms currently implemented in the cloud-based HICO Image Processing System (HICO IPS). Links to additional posts in this series describing the other algorithms are provided below. Here we provide an overview of the algorithm utilized for evaluating water optical properties in coastal and oceanic water.

HICO IPS

Objective – Retrieve water optical properties for coastal and oceanic water from hyperspectral imagery using a generalized multi-band algorithm.

Algorithm – Estimate water optical properties for absorption and backscattering (specifically, total absorption, phytoplankton absorption, detritus and gelbstoff absorption, total backscattering, and particle backscattering) using the Quasi-Analytical Algorithm (QAA v5; Lee et al. 2009, 2002).

Inputs – User specified HICO scene, with optional region-of-interest; optional NDWI land/water mask, with user adjustable NDWI threshold; and specification of desired optical property.

HICO IPS Turkish Straits

Output – Selected water optical property at 438 nm (m-1) depicted using a blue-red color ramp where blue represents low values and red represents high values. If the NDWI land/water mask was selected, then the selected optical property is only calculated and mapped for the water pixels.

HICO IPS Turkish Straits QAA

Try it out today for yourself: http://hyspeedgeo.com/HICO/

 

Related posts

Introducing the HICO Image Processing System

Calculating a land/water mask using HICO IPS

Deriving chlorophyll concentration using HICO IPS

Characterizing shallow coastal environments using HICO IPS

 

References

Lee Z, Lubac B, Werdell J, Arnone R (2009) An update of the quasi-analytical algorithm (QAA_v5), International Ocean Color Group Software Report, 9 pp.

Lee Z, Carder KL, Arnone RA (2002) Deriving inherent optical properties from water color: a multiband quasi-analytical algorithm for optically deep waters, Applied optics, vol. 41(27), 5755-5772.

Sunglint Correction in Airborne Hyperspectral Images Over Inland Waters

Announcing recent publication in Revista Brasileira de Cartographia (RBC) – the Brazilian Journal of Cartography. The full text is available open-access online: Streher et al., 2014, RBC, International Issue 66/7, 1437-1449.

Title: Sunglint Correction in Airborne Hyperspectral Images Over Inland Waters

Authors: Annia Susin Streher, Cláudio Clemente Faria Barbosa, Lênio Soares Galvão, James A. Goodman, Evlyn Marcia Leão de Moraes Novo, Thiago Sanna Freire Silva

Abstract: This study assessed sunglint effects, also known as the specular reflection from the water surface, in high-spatial and high-spectral resolution, airborne images acquired by the SpecTIR sensor under different view-illumination geometries over the Brazilian Ibitinga reservoir (Case II waters). These effects were corrected using the Goodman et al. (2008) and the Kutser et al. (2009) methods, and a Kutser et al. (2009) variant based on the continuum removal technique to calculate the oxygen absorption band depth. The performance of each method for reducing sunglint effects was evaluated by a quantitative analysis of pre- and post-sunglint correction reflectance values (residual reflectance images). Furthermore, the analysis was supported by inspection of the reflectance differences along transects placed over homogeneous masses of waters and over specific portions of the scenes affected and non-affected by sunglint. Results showed that the algorithm of Goodman et al. (2008) produced better results than the other two methods, as it approached zero amplitude reflectance values between homogenous water masses affected and non-affected by sunglint. The Kutser et al. (2009) method also presented good performance, except for the most contaminated sunglint portions of the scenes. When the continuum removal technique was incorporated to the Kutser et al. (2009) method, results varied with the scene and were more sensitive to atmospheric correction artifacts and instrument signal-to noise ratio characteristics.

Keywords: coral reefs; remote sensing; field spectra; scale; ecology; biodiversity; conservation hyperspectral remote sensing, specular reflection, water optically active substances, SpecTIR sensor

Figure 5. Deglinted SpecTIR hyperspectral of Ibitinga reservoir (São Paulo, Brazil) images and resultant reflectance profiles after correction by the methods of: (a) Goodman et al. (2008); (b) Kutser et al. (2009); and (c) modified Kutser et al. (2009).

Streher et al. 2015 Fig 5 Deglint