Applicability of low-resolution digital terrain models in preliminary forest road design: A case study in Knezevo, Bosnia and Herzegovina

This study examines the applicability of a coarse-resolution digital terrain model (DTM, 90?90 m) for preliminary forest road design in complex karst terrain. The research was carried out in the north-western section of the Forest Manage?ment Area ?Cemernica? (Knezevo, Bosnia and Herzegovina), where two design ap?proaches were compared: a DTM-based zero line traced on a digital contour map in QGIS, and a zero line established by direct field surveying. Both alignments were processed in RoadEng software to analyse geometric parameters, longitudinal pro?file, and earthwork volumes. The preliminary DTM-based alignment reached a length of 1,315 m, whereas the field-based alignment measured 1,333 m, coinciding along 964 m of their total length. Significant discrepancies were detected in earthwork quantities: 1,265 m? of excavation and 1,453 m? of embankment in the DTM-based design, compared to 1,979 m? and 3,012 m?, respectively, in the field-based design. These differences reflect the smoothing effect of low-resolution DTM data, which failed to capture microrelief variations typical of karst landscapes. The findings in?dicate that although coarse DTM may serve for preliminary route planning, it does not provide sufficient accuracy for reliable final design, confirming the necessity of high-resolution elevation data or detailed field surveying for forest road engineering in mountainous terrains.