Occurrence of Geothermal Features Based on Surface Roughness and Geobotanical Analyses derived by ALOS-2 PALSAR-2 and Sentinel-2 Images

Geothermal energy as renewable, reliable, and environmentally friendly is one of the most important energy resources. Based on government regulation about the National Energy Policy, the use of geothermal energy must reach 23% by 2025. This regulation is in line with the goal of the 7th of Sustainable Development Goals (SDGs). In order to achieve the government’s targets, a preliminary assessment on a wide scale by minimizing time consumption is necessary. Remote sensing technology utilizing radar and optic sensors promises as an alternative solution for preliminary surveys. The occurrence of geothermal system could be characterized by surface features associated with thermal system near the surface. Geothermal features originated from sub surface hydrothermal fluids to surface through fractures or pores in the rock formations. The chemical composition of the fluid composed by hot and acidic constituent affects the surrounding environment such as host rocks and vegetation. In this study, surface roughness and geobotanical analyses were used as indicator of geothermal features occurrence. The ALOS-2 PALSAR-2 and Sentinel-2 images were selected to calculate surface roughness and geobotanical anomalies including NDVI, GNDVI, SAVI, and RDVI, respectively. Combining ALOS-2 PALSAR-2 and Sentinel-2 images, we could characterize the occurrence of geothermal features by surface roughness more than 17.2 cm and the vegetation index less than 0.2. Accuracy of obtained occurrence map has been calculated about 71.43% with a predicting error rate of 28.57%. The likely prediction zones agreed to the up flow and discharge zones of geothermal system in selected study area.