The main topic of the work is the practical verification and evaluation of measurement and navigation accuracy of low-cost GNSS receivers under the canopy of trees in vegetation and out of vegetation period. The first chapter deals with forestry mapping and particular methods applicable in mapping of forest environment with the focus on the methods of determining location through GNSS in general. The second chapter characterizes used equipment and it is also focused on methodical procedure in data collection in terrain and subsequent office processing. The task of the final chapter is to demonstrate achieved results, to evaluate one another with their causes and to compare the accuracy of the particular devices. The main aim of the thesis is to evaluate the accuracy of the particular devices in spatial data collection and navigation under the canopy of trees and on the basis of achieved results, to evaluate the possibilities of the usage of low-cost GNSS receivers in forest environment.