The research described in this paper deals with the documentation of hiking trails in alpine areas. The study presents a novel research topic, applying up-to-date survey techniques and top quality equipment with practical applications in nature conservation. The research presents the initial part of the process—capturing imagery, photogrammetric processing, quality checking, and a discussion on possibilities of the further data analysis. The research described in this article was conducted in the Tatra National Park (TNP) in Poland, which is considered as one of the most-visited national parks in Europe. The exceptional popularity of this place is responsible for intensification of morphogenetic processes, resulting in the development of numerous forms of erosion. This article presents the outcomes of research, whose purpose was to verify the usability of UAVs to check the condition of hiking trails in alpine areas. An octocopter equipped with a non-metric camera was used for measurements. Unlike traditional methods of measuring landscape features, such a solution facilitates acquisition of quasi-continuous data that has uniform resolution throughout the study area and high spatial accuracy. It is also a relatively cheap technology, which is its main advantage over equally popular laser scanning. The paper presents the complete methodology of data acquisition in harsh conditions and demanding locations of hiking trails on steep Tatra slopes. The paper also describes stages that lead to the elaboration of basic photogrammetric products relying on structure from motion (SfM) technology and evaluates the accuracy of the materials obtained. Finally, it shows the applicability of the prepared products to the evaluation of the spatial reach and intensity of erosion along hiking trails, and to the study of plant succession or tree stand condition in the area located next to hiking trails.

Nowadays UAV photogrammetry becomes a common method for mapping and surveying. At the same time due to the increasing range of work carried out with UAV, the importance of final product accuracy increases. However to obtain survey-grade accuracy it is necessary to perform bundle adjustment processes that could be affected by multiple factors like unstable camera calibration, correlation between interior and exterior orientation and insufficient georeference information. One of the aims of the project was to prepare the terrestrial test field, which helps to obtain optimal decorrelation and allows to objectively assess the accuracy of the bundle adjustment in UAV application. During the project, two multi-variant flights over the test field were conducted. The flights were performed with a fixed-wing airframe equipped with PPK receiver on-board. Based on the conducted flights, many data sets have been prepared, which differ as follows: types of cameras, GSD, flight direction and georeferenced method.