The ruins of the St Catherine's monastery complex, the largest sacral ruins in Slovakia, are an important example of Slovak cultural heritage. The Franciscan monastery was a famous site of religious significance due to the legends describing the apparitions of St Catherine. The preservation project of the monastery remains started in 1994. As a part of this project, complex historical, archaeological, anthropological and geophysical research has been conducted at the site since 1997. Microgravity and ground-penetrating radar (GPR) surveys were carried out in the nave of the former church in order to reveal the position of three aristocratic crypts that served as burial places for the members or higher society in the seventeenth and eighteenth centuries. In the microgravity data processing, a novel method for the calculation of the building correction was employed, where the gravitational effect of the church is calculated using a polyhedral model of the building created from photographs with a special photogrammetric software. Several gravity anomalies were found in the residual Bouguer anomaly map. Semi-automated interpretation techniques including the Euler deconvolution and harmonic inversion have been used to investigate the depth and size of anomalous sources. Results from 36 GPR profiles obtained by a 400 MHz antenna were visualized in the form of horizontal timeslices and vertical time-sections. These images indicate anomalous reflections suggesting potential archaeological targets. Integrated interpretation of results from both geophysical methods has confirmed the presence of a known aristocratic crypt excavated in 2001, as well as two other crypts predicted from historical archives. The combination of microgravity and GPR surveys has proved to be a very effective and non-destructive tool for archaeological research.

Use of the microgravity technique for cavity detection in the exploration of historical buildings requires careful data acquisition and modern processing procedures. We have developed a new method for the calculation of building effects, where geodetic measurements and special photogrammetric software are used. In our new approach, a three-dimensional polyhedral model of an historical building is created from images using Eos System's PhotoModeler Scanner software. A comparison of equations for the calculation of the gravitational effect of polyhedral bodies is presented on a simple test model. The methodology of microgravity data processing is demonstrated on a small Slovak church, where two crypts were successfully detected using microgravity and GPR techniques in summer 2009. We have shown that close range photogrammetry methods offer a possibility to improve the microgravity data processing procedure.

Wooden trusses are a very specifi c object for measurement. They are often very complex and hard to reach; they are characterized by narrow spaces and low-lighting conditions. In recent years, laser scanning technology was mostly used for this task, because of its contactless nature, the possibility of measurement in the dark, and the robustness of the resulting 3D point clouds. Photogrammetry was mostly used in special cases, e.g., for the measurement of a few selected truss components, but not for the 3D modelling of an entire truss. However, the progress in computer vision algorithms is allowing us to accomplish image-based-modelling on very complex objects. The following contribution compares the point clouds of a wooden truss generated by the leading photogrammetry systems with a point cloud from laser scanning. The results confi rm the interesting potential of actual photogrammetric methods in the modelling of complex objects such as wooden trusses.

Mapping of debris flows by the morphometric analysis of DTM: a case study of the Vrátna dolina Valley, Slovakia The main objective of this contribution is to detect the morphogenetic processes by the numerical method of the differential geometry technique and compare the results with field surveying. The area of interest, the Vrátna dolina Valley, is located in the Malá Fatra Mountains in the northern part of Slovakia. Extensive mass movement deformations occurred in the surveyed area in 2014 induced by extreme precipitation events caused considerable damage. The Proxima software technology has been used to identify terrain elements using a precise digital terrain model (DTM) for the localisation of the debris flows head scarps. Precise DTM was derived from the airborne laser scanning (ALS) data. The morphometric analysis of landslide area was carried out on four selected locations. Verification of numerical mapping was performed by comparing results to the field survey data through visual comparison and area computation. Supplementary data was used in the form of orthophoto mosaics. The used spatial analysis applied on ALS data shows a high coincidence with the detection of the head scarps by field surveying, particularly in the hard to access and afforested areas. The main advantage of this approach lies in the reduction of field surveying and in the possible detection of the terrain changes not found during field surveying.