## 2 Materials and Methods
### Field Measurements  
The measurement was performed in this way to maintain the same conditions for all types of measurements regarding the layout of satellites, the quality of the internet signal, and the weather conditions. Field data were collected with a 3-component GNSS device, a UAV, and a total station. Field data was collected with a specific device to achieve the maximum accuracy that can be provided by that particular device while completing the targeted steps in the research itself. The GNSS device was the Stonex S900A model equipped with a high-performance 800-channel GNSS board. It can support all satellite constellations, such as GPS, GLONASS, BEIDOU, GALILEO, QZSS, and IRNSS, including L-band-Atlas corrections. It has an integrated E-Bubble sensor that allows measurement of inaccessible points with an inclined stick. It calculates the exact coordinate of the point by conducting measurements from 3 different positions. It is equipped with an optional IMU sensor with a tilt of up to 60\({}^{\circ}\)[27]. For the controlling receiver, a Stonex S40 controller with Android Cube 4.0 software was used. The UAV was DJI Phantom 4 PRO (software Pix4 dcapture for the fly mission) with a 3-axis-stabilized gimbal camera, a 20 MP 1\" CMOS sensor capable of shooting up to 4 K/60 fps video and photo bursts at up to 14 fps, and a Stonex R35L total station (software SurvCE) with a variable prism height of 2.0-4.6 m.  
Data for the research zone in the imaginary profiles of the forest/skid road were recorded approximately every 10-15 m and at 4-6 points in the terrain breaks to obtain a sufficiently accurate configuration of the recorded road (Figure 3). The GNSS receiver was switched on outside the forest to avoid cold-start problems [28], and it was configured to store data only in the FIX mode.  
Figure 2: Data flowchart from stages of surveying field data to the final proof/refutation of hypotheses.  
GCPs for positioning purposes in the process of processing aerial images were measured using the GNSS device and corrected with a total station (it was used with an angular accuracy of 5\" and a distance accuracy of \(\pm\)2 mm + 2 ppm), so this method practically works independently of forest conditions and therefore guarantees reliable results [29]. The total station was used only for providing control and possibly for correcting the position of the GNSS points, i.e., it was used if necessary to make any horizontal or vertical corrections with respect to the GCPs themselves due to possible deviations in the GNSS recordings. A total of 14 GCPs were recorded (shapes in the form of a cross of approx. 50 \(\times\) 50 cm were used for GCP markings) (Figure 4). GCPs were used solely for georeferencing and were not used in the final analysis for point comparisons [30].  
The last survey of the road was carried out by a UAV, where aerial photos were collected with an overlap of 80% from a height of 50 m. Two missions were conducted that covered the entire research area, and the UAV was kept at a stable height according to the starting point, mostly due to limited battery life. Postprocessing was performed using the Pix4 Dmapper program, and the general parameters of the recording and the obtained data after processing in the program are shown in Table 1.  
Figure 3: Positions of recorded terrain points in profiles and GCPs.