Potential of Low-Cost UAV Photogrammetry for Documenting Hard-to-Access Interior Spaces Through Building Openings

Unmanned aerial vehicles (UAVs) are primarily used in the field of cultural heritage for mapping the exteriors of larger objects and documenting the roofs and façades of tall structures that cannot be efficiently or feasibly measured using conventional terrestrial technologies and methods. However, due to the considerable diversity of cultural heritage, there are practical demands for the measurement of complex and inaccessible objects in interior spaces. This article focuses on the use of two different off-the-shelf UAVs for partial photogrammetric reconstruction of the attic of a mining house, which was only visible through a window in the gable wall. Data from both UAVs were compared with each other and with terrestrial laser scanning. Despite the lower quality of the results from the DJI Mini 4 Pro compared to the DJI Mavic 3 Enterprise, the results from both UAVs would still be suitable for documenting the interior attic spaces. However, a detailed analysis of the photogrammetric data indicates that, when selecting a UAV for this purpose, it is necessary to consider the limitations of the camera system, which may lead to a reduction in the geometric accuracy and completeness of the point clouds.