Spatiooral analysis of the direction of Merapi volcanic eruption in 2010 and 2020

Major problems related to mapping activities in developing countries is lack and out of date spatial data. Although, spatial data is paramount important as a basis for decision-making. The same case occurs at Merapi volcano which often requires urgent decisions by local authorities based on spatial data of geological disasters. This study aims to build spatiotemporal data of pyroclastic deposits, and to determine the direction and the extent of pyroclastic deposits as well. The methodologies were focused on image interpretation, virtual fieldwork, and accuracy assessment. The preprocessing of remote sensing images included a radiometric correction and image sharpening. Radiometric correction was implemented to convert the original image value to the Bottom of Atmosphere (BOA) reflectance value. Due to the COVID-19 pandemic, fieldwork could not be conducted, hence we replaced it using virtual fieldwork in order to classify objects on Landsat satellite imagery manually. After the virtual fieldwork, we analyzed the direction and the area of pyroclastic deposits in order to produce a map of pyroclastic deposits of Merapi Volcano. The result indicates that the pyroclastic deposits of the Merapi Volcano in 2011 were spread to the southeast, west and north. While in 2020, the deposits were directed to the west. The sediment area is 39.935.176 m2 in 2011 and 7.772.015 m2 in 2020. The result can be used to support decision-making by authorities and stakeholders in this volcanic area. © 2021 SPIE.