## 3 Results  
In sum, 29 profiles (10-15 m apart) were defined in the field to measure the design zone (3D terrain) of the future forest/skid road with a GNSS device with 4-6 points in each profile. A total of 14 GCP points were defined for the precise processing of aerial images. The total length of the route was 542.55 m on sparsely vegetated and non-vegetated forest land. Later in the design program, in order to obtain more detailed drawings and a more significant number of cross-sections for comparing the masses of excavations and embankments, 54 profiles (approx. every 9-10 m) were formed to illustrate the parameters of the designed forest/skid road. The products of data processing were DTM (digital terrain model), DSM (digital surface model), and an orthomosaic of the researched area (Figure 4). A total of 140 points were compared using DTM and DSM data from the same positions to compare them with GNSS height points. The compared and tested elevation data are presented with descriptive statistics (Table 2). The analysis of variance (Table 3) revealed a significant statistical error between a certain group of height data, and to determine whether there was a deviation between all groups or only certain pairs, a post hoc Tukey HSD test was performed (Table 4). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Unweighted Means**} \\  & & \multicolumn{2}{c}{**Current Effect: F(2, 280) = 7.9914, \(p\) = 0.00042**} \\ \hline
**Data Source** & **Mean** & **Std. Err.** & \(-\)**95.00\%** & **+95.00\%** & **Number** \\ \hline GNSS & 607.4508 & 0.227205 & 607.0016 & 607.9000 & 141 \\ DSM & 607.5205 & 0.227373 & 607.0710 & 607.9701 & 141 \\ DTM & 607.4762 & 0.225574 & 607.0302 & 607.9222 & 141 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Descriptive statistics of the tested elevation points. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **SS** & **Degr. of Freedom** & **MS** & **F** & \(p\) \\ \hline Intercept & 156,101,808 & 1 & 156,101,808 & 7,194,011 & 0.00000 \\ Error & 3038 & 140 & 22 & & \\ Elevation & 0 & 2 & 0 & 8 & 0.000422 \\ comparison & Error & 6 & 280 & 0 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of the analysis of variance for height points measured by GNSS, DTM, and DSM. The results of the post hoc test indicate that there is no statistically significant difference between the height data of GNSS and DTM, while the difference between GNSS and DSM is significant, and these data cannot be used for further analysis or for creating a detailed main project in the design program for forest/skid roads. Based on GNSS and DTM elevation points, the main detailed projects were carried out, and leveling was formed by using the reference data (GNSS data 3D terrain model) in the CESTA program for the design of forest roads. After that, only field data were replaced with a DTM 3D terrain model, while leveling did not change its shape or height position. A forest/skid road with eight horizontal curves was designed (minimum radius of 20 m and maximum radius of 700 m). The level is formed by 12 breaks (changes in slope), i.e., 13 sections of different longitudinal slopes. The minimum longitudinal slope ranges from 0.79% to a maximum longitudinal slope of 9.89%. As shown in Figure 5, when replacing the 3D terrain model with two different methods for obtaining height points, there are no significant changes, and during the design stage, there was no need to change the level. The average deviations were 0.02 m, which is not significant for the change in the level's position. This confirms hypothesis 1, and we can state that if it is observed only in the longitudinal section, that is, the 2D view in the height sense, there are no significant changes in the terrain characteristics of the data recorded by GNSS- and UAV-processed data. The only significant deviation, which was obtained in profile 9, is 19 cm. Still, the leveling appearance does not need to be changed due to only one deformation in the terrain.