Since the launch of the IKONOS-1 in 1999 and several other following commercial satellites, High Spatial Resolution (HSR) satellite images have been widely used for topographic mapping, Digital Elevation Model (DEM) data generation, and urban and land cover classifications. On the other hand, it has been relatively rare to find quantitative applications for extracting biophysical parameters from HSR images.Although there have been a few cases of using HSR images to extract information regarding the physical conditions of vegetation (Imukova et al., 2015;Pu and Cheng, 2015;Tillack et al., 2014;Sprintsin et al., 2007) and water quality (Choe et al., 2015; Chang et al., 2009)
Department of Geoinformatic Engineering, Inha UniversityAbstract : Atmospheric correction is an essential part in time-series analysis on biophysical parameters of surface features. In this study, we tried to examine possible problems in atmospheric correction of multitemporal High Spatial Resolution (HSR) images obtained from two different sensor systems. Three KOMPSAT-2 and two IKONOS-2 multispectral images were used. Three atmospheric correction methods were applied to derive surface reflectance: (1) Radiative Transfer (RT) -based absolute atmospheric correction method, (2) the Dark Object Subtraction (DOS) method, and (3) the Cosine Of the Uun zeniTh angle (COST) method. Atmospheric correction results were evaluated by comparing spectral reflectance values extracted from invariant targets and vegetation cover types. In overall, multi-temporal reflectance from five images obtained from January to December did not show consistent pattern in invariant targets and did not follow a typical profile of vegetation growth in forests and rice field. The multi-temporal reflectance values were different by sensor type and atmospheric correction methods. The inconsistent atmospheric correction results from these multi-temporal HSR images may be explained by several factors including unstable radiometric calibration coefficients for each sensor and wide range of sun and sensor geometry with the off-nadir viewing HSR images.Key Words : Atmospheric correction, high spatial resolution, calibration coefficients, multi-temporal, surface reflectance, KOMPSAT, IKONOS
Atmospheric Correction MethodsAtmospheric correction of optical imagery is mainly to derive purely reflected portion of energy from the atsensor radiance (Lt) by removing the amount of radiance influenced by atmospheric effects. The radiance (Lt) received on-board sensor can be expressed in a simple form of equation (Eq. 1) and atmospheric correction is the process of extracting surface reflectance (ρ) from Lt.where ρ = surface reflectance, E = solar and diffuse irradiance on surface, T = transmittance of atmosphere, and Lp = path radiance.Atmospheric correction methods of optical imagery can be divided into two major categories by means of obtaining the unknown variables of T and Lp in (Eq. 1).Absolute atmospheric correction is based on the calculation of physical processes of radiative trans...