Multi-Angle Observation of the Geothermal Area in the Hakone Volcano (Owakudani) Using an Airborne Sensor (STIC: Arts-Se‘s Camera Systems)

We propose a method to estimate the brightness-temperature distribution under fumarolic gas in a geothermal field using the multi-angle observation image data set from the ARTS-SE camera system, the Structure and Thermal Information Capture (STIC). We report results of data analyses for the geothermal area in the Hakone Volcano (Owakudani) using visible and infrared (IR) images from STIC. The STIC's IR cameras quantitatively estimated the surface structures (DSM) using Structure from Motion and Multi-View Stereo (SfM/MVS) processing with errors of ±4 to 12m in the horizontal direction and 30m in the vertical direction (10m or less excluding local sites). Using the result from this processing, we obtained multi angle (observation angle of 0 to ± 9.5°) orthorectified ground-surface brightness temperature 20 images of the 15-1 crater in Owakudani from the 20 continuous images of STIC's IR camera images. We estimated the maximum brightness temperature and heat radiation rate of the 15-1 crater using a square area of 30x30m including the 15-1 crater in these 20 consecutive thermal IR images (measurement interval 0.5s). Those estimated values fluctuated by ± 50% during the observation for a total of 9.5s because of large amounts of fumarolic gas. These results suggest that STIC's IR cameras can be used to detect ground-surface brightness temperature distribution that is affected by fumarolic gas in a volcanic geothermal area more accurately than conventional one-shot observation.