Examining the accuracy of DEM of difference and 3D point cloud comparison methods: Open pit mine case study

Authors : Nilüfer Özdaş, Mehmet Güven Koçak, Serkan Karakış

Pages : 41-50

Doi:10.9733/JGG.2024R0004.E

View : 105 | Download : 115

Publication Date : 2024-05-03

Article Type : Research Paper

Abstract :With the widespread use of unmanned aerial vehicles (UAV), high-accuracy photogrammetric mapping studies can be carried out over small areas with cost-effective simple systems. By comparing images obtained at different epochs, 3 Dimensional (3D) change detection studies can be easily performed. Digital surface models (DSM) are obtained from the point cloud (PC) with the processing software, their differences are taken, and temporal changes can thus be modeled. This method is known as DEM (DSM) of Difference (DoD) in practice and has low computational cost. Recently, with the availability and accessibility of powerful computers capable of processing increasing amounts of data, 3D change detection studies can be performed directly with raw PCs without converting them to DSM. Methodologically, DoD and PC-based analysis strategies have different evaluation stages and outputs. With DoD, only changes in the vertical direction can be revealed, while PC comparison methods can produce the 3D change vector. In this study, the well-established DoD method and Multiscale Model-to-Model Cloud Comparison (M3C2), one of the 3D PC comparison methods, were compared. The accuracy of the methods was tested at an active open pit mine site where intensive excavation works have been undertaken. Standard deviation values were found below 11 cm with M3C2 distance and DoD differences obtained from UAV images having average ground sampling distances (GSD) of 5.8-6.9 cm. Only about 1% of the differences were categorized as outliers.
Keywords : 3B nokta bulutu, Sayısal yüzey modeli, Fark SYM, M3C2, Doğruluk