The bathymetry of coral reef area at Bonetambung Island (optical and hydroacoustical comparison to nautical chart)

Abstract

Base-on time efficiency, cost, and wide coverage area, bathymetry mapping with a hydroacoustic measurement on a small island were avoided; only remote sensing surveys were conducted. Therefore, comparing the bathymetry map of Bonetambung Island, from Hydroacoustic data with that from Landsat 8 OLI images, is essential. Hydroacoustic measurements were carried out in September 2013, while Landsat 8 Satellite Imagery was recorded on April 25, 2018. After being corrected, Kriging (K) and Natural Neighbor (NN) interpolations methods were performed on both data. The 95% ANOVA test, conducted in a previous study, showed that the average depth for the two interpolation results did not differ significantly for the depth range of 0-5m. However, for the 0-30m depth range, this study shows that the accuracy of interpolation hydroacoustic data is much better with the range of RMSE = 0.8-1.2m, ME = 0.4-0.7m, and range of RMSE = 0.8-1.3, ME = 0.4-0.7 for each K and NN interpolation methods. On the other hand, only in the depth range of 0-5m, the accuracy of interpolation Landsat 8 OLI data shows a relatively good value with RMSE = 1.1m, ME = 0.8m, and RMSE = 1.1m and ME = 0.8m for the K and NN Methods respectively. The results of hydroacoustic data interpolation and Landsat 8 OLI were then visually compared with Dishidros Nautical chart number 124. It was concluded that although Landsat data can produce bathymetry maps with a wider coverage area, its accuracy is still unreliable compared to bathymetry maps from Hydroacoustic measurements.