Comparison of Non-Contact Measurement Technologies Applied on the Underground Glacier—The Choice for Long-Term Monitoring of Ice Changes in Dobšiná Ice Cave

Because of the international significance of Dobšiná Ice Cave (Slovakia), it is important to have proper data about the state, movement, or decrease of the ice in which various information about past environments can be preserved. Thus, the goal of the study is to find out which of the 3D scanners used here is the most suitable for long-term monitoring of ice changes. A comparison of the 3D point clouds acquired from laser scanners Leica C10 and Leica RTC360 and the mobile scanners GeoSLAM Zeb Horizon and the iPhone 14 Pro to reference clouds from photogrammetry or tacheometry is provided, and also the process of data acquisition and registration is described. To catch the differences in point clouds according to different types of ice, cross-sections of the vertical and layered ice wall, horizontal ice surface, and artificial ice tunnel are analysed. Some remarkable but also unwanted properties of 3D scanners have been concluded, and the best compromise for 3D scanning of this ice cave has been chosen. According to the diversity of ice types and different layers occurring in Dobšiná Ice Cave, results could be partially helpful in choosing a suitable measurement technology for ice in other caves worldwide.