Rapid mapping of slope hazards with photos acquired from a low-cost unmanned aerial vehicle using the automatic mission planning and image processing system (AMPIPS) - Examples of Namasha and Laonung areas

Slope hazards are destructive geological processes that cause enormous damage to human settlements, roads, infrastructure, and other valuable resources. Triggered by earthquake or heavy rainfall, the slope hazards are usually occurred in hilly regions over large areas yet within short period of time. Rapid mapping of the slope hazards is therefore a crucial task for disaster mitigation, assessment and relief. Among the general air-borne and space-borne platforms, the unmanned aerial vehicle (UAV) provides an innovative approach that is much cheaper, safer and more flexible to be deployed in a small area, ranged from a few to tens of square kilometers. Even on a overcast day, flying an UAV at low altitude is still able to give us a good dataset for mapping the disaster area. However, there is a significant gap in recording the accurate position and attitude data during an UAV flight mission. As a result, a lot of UAV platforms are limited to qualitative applications using non-georeferenced photos. Thanks to our recent progress in developing the automatic mission planning and image processing system (AMPIPS), we successfully employ a low-cost UAV in Namasha and Laonung areas to acquire tens of photos from approximately 800 meters. Comparing to the control points extracted from the base image, the accurate position and attitude of camera can be accurately derived when each photo is shot. Together with the digital topography model, the standard procedure of orthorectification can be applied to process each photo. All orthorectified photos are then stitched to a seamless and color-balanced mosaic and published onto Google Earth. This research demonstrates that the orthorectified image of slope hazards can be rapidly generated using a low-cost UAV with AMPIPS, and the result can be shared and browsed in 3D fashion through the internet.