Sentinel-2 image transformation methods for mapping oil spill – A case study with Wakashio oil spill in the Indian Ocean, off Mauritius

Abstract

Although several indices have been constructed and available at the Index database (IDB) for Sentinel-2 satellite to map and study several earth resources, no indices have been developed to map oil spill. We constructed band ratios (5 + 6)/7, (3 + 4)/2, (11+12)/8 and 3/2, (3 + 4)/2, (6 + 7)/5 using the high-resolution MSI (multi-spectral instrument) visible-near infrared-shortwave infrared spectral bands of Sentinel-2 by summing-up the bands representing the shoulders of absorption features as numerator and the band located nearest to the absorption feature as denominator to discriminate oil spill, and demonstrate the potential of this method to map the Wakashio oil spill which occurred in the Indian Ocean, off Mauritius. The resulted images discriminated the oil spill well. We also decorrelated the spectral bands 4, 3 and 2 by studying the spectral band absorptions and discriminated the spill as very thick, thick and thin. The results of decorrelation stretch method exhibited the distribution of types of oil spill in a different tone, distinctly. Both the image transformation methods (band ratios and decorrelation stretch methods) showed their capability to map oil spills, and these methods are recommended to use for similar spectral bands of other sensors to map oil spills. This study demonstrated the application of band ratios and decorrelation stretch methods to map oil spill. The methods discriminated the oil spill off Mauritius, and showed spill thicknesses from the Sentinel-2 data. The new methods are recommended to use for the spectral bands of other sensors to map oil spill.

Using Sentinel-2 imagery for detecting oil spills via spatial roughness of mixed normalized difference index

“…In this section, we demonstrated our proposed index and its roughness results for all study images compared with the feature images of the valuable research expressed in (1) 18 and the observation images of Rajendran et al research 7 . Figure 3 illustrates the experimental results for all study areas.…”

“…Rajendran et al 7 , developed two false-color composite images based on the band ratios for the Sentinel-2 data. For the first image, the RGB values were instead of (B5+B6)/B7, (B3+B4)/B2, and (B11+B12)/B8, respectively.…”

“…Moreover, it can also detect oil spills despite the poor atmospheric conditions 6 . However, SAR data was difficult to separate between the oil spill and false targets that so-called "lookalikes" 7 . The optical sensor data gives the advantage for the identifying capability from the spectral signature 8 .…”

Assessing LAPAN-A3 Satellite with Line Imager Space Application (LISA) Sensor for Oil Spill Detection

“…This unique property of oil can be studied, especially when it interacts with light and satellite sensors receive it. Oil has a higher emissivity than water, so when it is exposed to sunlight, it emits infrared radiation [19]. The oil layer that is exposed to sunlight will emit infrared radiation.…”

“…Determination of band combination is one commonly used method for detecting oil spills. Previous studies, such as those of Kolokoussis and Karathanassi [17] and Rajendran et al [19], used Sentinel-2 and multiple band combinations. The NIR-Red-Green band combination is commonly used in developing false-color composites (FCC), while the Red-Green-Blue band can help distinguish oil thickness LAPAN-A3 (LA3) is the latest generation satellite belonging to Indonesia and was successfully launched in June 2016.…”