SHALLOW WATERS DEPTH ESTIMATION USING EMPIRICAL SATELLITE DERIVED BATHYMETRY AND SENTINEL-2 DATA, CASE STUDY: EAST COASTAL WATERS OF JAVA ISLAND

Abstract. Hydrographic survey is an activity to provide spatial information in the marine sector. To produce accurate data, hydrographic surveys require very large costs. With the vast sea area in Indonesia, this becomes a very big challenge. In addition, there are some areas that cannot be reached by survey vessels (limited to a depth of > 25 m). Therefore, an alternative method is needed to provide bathymetry data in Indonesia. There is a new technique that is being developed and does not require high costs to obtain water depth data, by using remote sensing technology, especially by using passive sensor image technology. This technique or method is known as Satellite Derived Bathymetry (SDB) which can estimate depths of up to 30 meters. The SDB technique which is often used is empirical SDB. The empirical SDB has the principle of connecting the spectral value of the image with the measured depth. With the use of Sentinel-2 satellite imagery which has high temporal and spatial resolution, the SDB capability is expected to be improved. East coastal waters of Java Island are in the Bali Strait. This strait separates the island of Java from the island of Bali. In the Bali Strait there is a busy ferry shipping lane and there are also underwater cables used to supply electricity to Bali Island from Java Island. On the Java side, there are also many beaches and underwater tourism that must be preserved. Therefore, it is very important to be able to know the hydrographic data such as bathymetry data in the east coastal waters of Java Island. The objective of this work is thus to estimate shallow water depths using empirical SDB and Sentinel-2 images in the east coastal waters of Java Island. With two band combinations applied in the algorithm, best combination to produce the best depth map for the study area can be obtained. Comparing with reference data, the results show Band 1&3 combination give the better correlation and RMSE (0.76 and 0.026) than Band 2&3 combination (0.64 and 0.075).