This diploma thesis deals with the description and study of the performance of free mobile apps. More precisely, it examines the efficiency of apps enhanced with the global positioning technology GNSS, which are utilized as an aid in athletic training. In the first part of the thesis, a brief description of smartphones and their development is presented, followed by an outline of some mobile apps with useful features. In the empirical section, the focuss is given on the analysis of the different lengths and heights measured with various smartphone apps. In addition, these results were also contrasted with data that was acquired with manual GNSS receivers and a bicycle computer. The measured horizontal lengths from the GNSS receivers were then compared with the lengths obtained from large-scale national maps and orthophoto. In order to contrast the calculated height differences, DEM and largescale national maps were employed. Further clarification is given on how apps calculate height differences.