Application of unmanned aerial vehicles (UAVs) for generating high-resolution intertidal DEM

Abstract

Recently, the UAVs have been widely used in aerial survey. UAVs are classified into rotary wing and fixed-wing type. In order to demonstrate the suitability of UAVs to the tidal flat study, we tested fixed-wing UAV mounted with Canon S95 and rotary-wing UAV mounted with Canon 6D. For the accurate geometric correction, it is necessary that pre-processing and post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous d rotary-wing UAV mounted with Canon 6D. For the accurate geometric correction, it is necessary that pre-processing and post-processing of the obtained image. The interior and exterior orientation parameters were obtained based on the lens distortion model. For the accurate mosaic image generation, the topographic height of the tidal flat was measured using RTK-GPS and flight plans were prepared to obtain 70% image overlap to the azimuth direction and 40% to the range direction. For the mosaic image based on the rotary-wing UAV, waterlines were extracted from each image, and DEM was generated using a waterline method. For the mosaic image based on the fixed-wing UAV, DEM was obtained by aerial triangulation when tidal flat was fully exposed. The accuracy of DEM from fixed-wing UAV was higher than that from rotary-wing UAV. The Fixed-wing UAVs have a limitation to mount various cameras such as DSLR. However, the rotary-wing UAVs can mount not only high-resolution optical cameras such as DSLR but also multispectral, hyperspectral and thermal sensors. In conclusion, the fixed-wing UAVs are advantageous for the analysis on topographic changes, and the rotary-wing UAVs are advantageous