Cross-Polarized SfM Photogrammetry for the Spatial Reconstruction of Challenging Surfaces, the Case Study of Dobšiná Ice Cave (Slovakia)

Geodetic methods are integral to mapping surface and subsurface objects phenomena. Modern geodetic technologies such as laser scanning digital photogrammetry have also become a standard part of the documentation cave spaces. In some cases, these cannot accurately capture measured thus provide reliable data. One example is ice with specific characteristics in caves deposits. world’s most studied Dobšiná Ice Cave (Slovakia), which has undergone significant changes ice-filling area volume recent years. To monitor analyze all properly, we need know this mass it regularly. Where modern terrestrial (TLS) or may fail due ice’s physical properties, propose using cross-polarized Structure-from-Motion (SfM) photogrammetry. As case study, method was used 28 m long tunnel cave. Two polarizing filters (on flash light source on camera lens) were 90° rotation each other achieve cross-polarization effect remove reflections. This removed reflections, giving us compact accurate point cloud entire tunnel. The dense from (CP) denser more does not contain many outliers noise points when compared non-cross-polarized (non-CP) TLS covers without holes; however, penetration beam through makes unusable. Only CP densely enough additional noise. methodology can then be parts geomorphological applications suppress reflections so high-quality results for further processing analysis obtained.