The free and open access optical sensor data from the Sentinel-2 constellation can be used for supporting the operation of oil spill monitoring. It has several spectral bands from visible to shortwave infrared with medium to high resolution, which is suitable for detecting the oil spills. However, the spectral signature of the oil spill often has similar to the surrounding environment. Moreover, it also depends on many parameters, such as sensing angle, sea depth, wave characteristics, etc. In this paper, we propose the method for detecting the oil spill by using the Sentinel-2 images. It is based on the Mixed Normalized Difference Index (MNDI) derived from the Normalized Difference Vegetation Index (NDVI) and the Reversed version of the Normalized Difference Index (NDI) applied for the forest fire monitoring. This index will give the high variation values in the oil spill area, which can estimate the oil spill area by observing its spatial roughness. Four study areas in Saudi Arabia, Greece, Azerbaijan, and Indonesia were used to evaluate the detectable performance compared with the current methods. The visualized results show that our algorithm gives noticeable results and high contrast, including low noise, except the oil spills in Greece.
In this paper, we present two approaches for net Point Spread Function (net-PSF) estimation of Thailand Earth Observation System (THEOS) imaging system. In the first approach, we estimate the net- PSF by employing the specification information of the satellite. The analytic model of the net- PSF based on the simple model of push-broom imaging system. This model consists of a scanner, optical system, detector and electronics system. The mathematical PSF model of each component is demonstrated in spatial domain. In the second approach, the specific target images from THEOS imaging system are analyzed to determine the net-PSF. For panchromatic imaging system, the images of the checkerboard target at Salon de Provence airport are used to analysis the net-PSF by slant-edge method. For multispectral imaging system, the new man-made targets are proposed. It is a pier bridge in Lamchabang, Chonburi, Thailand. This place has had a lot of bridges which have several width sizes and orientation. The pulse method is used to analysis the images of this bridge for estimating the net-PSF. Finally, the Full Width at Half Maximums (FWHMs) of the net-PSF of both approaches is compared. The results show that both approaches coincide and all Modulation Transfer Functions (MTFs) at Nyquist of both approaches are better than the requirement. However, the FWHM of multispectral system more deviate than panchromatic system, because the targets are not specially constructed for estimating the characteristics of the satellite imaging system.
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