Semi-automatic shoreline extraction using water index transformation on Landsat 8 OLI imagery in Jepara Regency

Abstract

Oceanographic conditions, physical development, cultivation, and sedimentation in river estuaries are dynamic trends occured in Jepara Regency. These dynamics need to be understood so it is necessary to determine the position of the shoreline as an impact of morphodynamic to see the latest variations of the shoreline in Jepara Regency. Landsat imagery can be an alternative source of data for shoreline mapping, while shoreline extraction methods can be conducted using water index, which is easy to perform. Regulation published by the Head of the Geospatial Information Agency Number 6 of 2018 can be used as a standard for shoreline maps accuracy obtained from remote sensing imagery. The research objective is to map the Jepara shoreline using NDWI, MNDWI, and AWEI transformations and compare the water index performance. Shoreline data is extracted from Landsat 8 OLI imagery, while the reference shoreline for accuracy assessment is obtained from visual interpretation of PlanetScope imagery. Threshold 0 and subjective threshold based on experiments per coastal physical typology samples are used to separate land-sea. The difference in the shoreline length on the eight shorelines are due to the limited capability of the water index in obtaining the shoreline. MNDWI shoreline with a threshold of 0 gives the lowest RMSE value (RMSE= 25,33 m) among another index, while the NDWI shoreline with a threshold of 0 gives the highest RMSE value (RMSE= 43,77 m).