Radiation dose rate mapping based on attenuation coefficients for forest area in UAV sensing

Changing amount of radiation dose has been a great concern by citizens near the difficult-to-return area after the Fukushima Daiichi nuclear disaster. Rigorous assessment of public safety including inaccessible forest areas at a meter level is one of the keys in the disaster recovery plan. Each measurement point near the ground surface in UAV-based sensing is exposed from the effects of radiation emission from various angles in the fields including forest and plain, and thus acquisition of the attenuation coefficients on site is not realistic by simply using the spatial integration of point-kernels or exponential decay functions. The proposed method in this paper utilizes the vertical and horizontal distance correction. The field test at a residence in the forests near the difficult-to-return area was performed, and in this area we found the improvement of 42% in RMSE (root mean squared error) from the results of a base model. Importantly, the experimental result suggested that the proposed method has the potential to efficiently accept using the different measurement data, both measured points near the ground surface and the flight heights during the UAV sensing. (author)