UAS Photogrammetry Applications in Environmental Engineering—A Study Case of Dead Trees Statistics at Gwydir Wetlands

Unmanned aerial system (UAS) photogrammetry has been widely adopted in aerial mapping and 3D modelling for various applications. In environmental engineering, UAS photogrammetry has been utilized for the extraction of vegetation information based on photogrammetric raster images. Images collected by UAS will be used to generate textured 3D point cloud and ortho-images. The photogrammetric software Pix4D is applied in this study. Corresponding environmental indicators can be conveniently extracted from ortho-images. Vegetation information can also be extracted by processing these indicators. At present, a more commonly application of vegetation information extraction method is spectral analysis method, that is, analyzing the bands in the RGB image for screening. Color grading to classify as a new method will be given and will be compared to spectral analysis.