2018 Volume 34 Issue 2 Pages 41-47
Measures for restoring farmland damaged in the 2016 Kumamoto Earthquake vary according to the degree of damage. Therefore, we investigated the damage caused by the 2016 Kumamoto earthquake to the surface of the farmland using drones. We made three-dimensional models using SfM, MVS processing on drone aerial images and made DSMs by calibrating altitude levels with Geographical Survey Institute and ground surveying results together. As a result, it was possible to measure the quantity of unevenness (difference from a mean altitude level of the farmland ground). After comparing it with the airborne laser surveying, the quantity of unevenness which drones measured had the high precision that a meaningful difference was not recognized. On the other hand, the measurement cost of the drone in this case is about 1/3 of the airborne laser surveying, and there are advantages that drone observation is possible more quickly, more conveniently. Furthermore, we investigated a cause of the wavy surface confirmed by drone observation. Aerial photographs from 1962 showed that the unevenness corresponded with creeks buried by infrastructure maintenance. We reveal that the 2016 Kumamoto earthquake caused the creek part to sink.
