Trails that were drawn on the forestry map beforehand represent a solid basis for a detailed silvicultural planning and forestry work performance. In practice, there are discrepancies between the GPS measurement method and the terrestrial measurement of the trail condition. The field part of the Diploma thesis was carried out in the Forestry Unit (FU) Črmošnjice, Section 1. The relevant section falls within the forestry management class of Dinaric fir-beech forests occupying the best sites at 830-910 metres above sea level. In the section, we measured all trails using both the GPS and the terrestrial measurement methods. The trails were measured by these methods simultaneously. We compared the differences between the measured trail lengths and the openness of forests. All data were processed using the MapInfo Professional 11.5 software, where the trails measured by the terrestrial method were added trails where we also considered magnetic declination. With the terrestrial method, we measured a total of 155.41 m/ha of trails in the section, which represents a 76.07-percent openness of the section, whereas with the GPS method, we measured a total of 161.83 m/ha of trails, representing a 79.55-percent openness of the section. While the GPS method is relatively accurate if the signal reception is good, the terrestrial method takes longer and requires an assistant, but it is far more accurate than the GPS method. For forestry purposes, the GPS method is accurate enough for forest trail measurements. Using both methods we have come to the conclusion that the openness of the section is barely satisfactory.
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