# The Influence of the Quality of Digital Elevation Data on the Modelling of Terrain Vehicle Movement
## 3 Results
### Comparison of the Accuracy of Digital Terrain Models Using Raster Passability Analysis  
Properties of digital terrain models can also be studied from the view of their use in the decision-making processes of commanders and staff. Data properties are evaluated from the area difference in the calculated passability. A difference was given by comparing selected models with the most detailed data (e.g., the difference between DTM 3 and DTM 5). Each pixel was assigned one of three passability values (GO, SLOW GO, NO GO) according to the parameters calculated from the traction curves of selected vehicles. For the calculation of the parameters, see [16]. This was based on the findings of the evaluation of dynamics of vehicle movement in the terrain of [46; 47]. A total area of all pixels was then converted to percentages of passable, hardly passable, and impassable terrain. Map comparisons of the results of CCM analysis for the T815 vehicle and all tested terrain models are shown in Figure 8. A summary of passable area deviations between lower detail models and DTM 5 is displayed in Table 4.  
Figure 8: \(Cont.\)  
The raster analysis of passability produce the following results:  
1. Deviations in passable area (GO): * The more detailed the model of terrain, the smaller the passable area. * The passable area of 851 ha (out of a total of 900 ha of one 3 km \(\times\) 3 km area) in DTM 5 represented * 860 ha in DTM 4 (1% larger passable area); * 870 ha in DTM 3 (2% larger passable area); * 880 ha in DTED 2 (3% larger passable area). * These ratios may significantly vary in different types of landscape (mountains) or surface conditions (impassable soils) but have the same trend. 2. Deviations in the hardly passable area (SLOW GO): * The position and structure of hardly passable area remained unchanged in all models. 3. Deviations in the impassable area (NO GO): * The total area of impassable territory increased with the detail of a used model. * The impassable area in DTM 5 (15 ha) represented \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**CCM Parameters**} & \multicolumn{3}{c}{**Average Deviations of Passable Area in Comparison with DTM 5 (\%)**} \\ \cline{2-4}  & **DTM 4** & **DTM 3** & **DTED 2** \\ \hline T815 GO moist (max slope = 6.25\({}^{\circ}\)) & 1.32 & 2.71 & 4.39 \\ T815 GO semi-moist (max slope = 12.08\({}^{\circ}\)) & 1.31 & 2.54 & 3.32 \\ LRD GO dry (max slope = 16.17\({}^{\circ}\)) & 1.11 & 2.32 & 3.45 \\ LRD GO + SLOW GO semi-moist (max slope = 21.82\({}^{\circ}\)) & 0.77 & 1.83 & 2.37 \\ BVP2 GO + SLOW GO semi-moist (max slope = 28.81\({}^{\circ}\)) & 0.33 & 0.98 & 1.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average deviations of the passable area calculated from elevation models (DTM 4, DTM 3, DTED 2) in comparison with DTM 5 with different parameters (vehicle type, humidity); results are mean values for five 3 km \(\times\) 3 km areas, max-maximum available slope for the respective conditions, 1% deviation of the area means 9 netares out of 900 hectares of one area and area deviations of elevation models with DTM 5 are always positive (larger passable areas). Figure 8: The result of the cross-country mobility analysis of a selected locality for the vehicle T815. A detailed look at a selected valley in the Dobruska locality. Testing was done with the method of raster analysis of the evaluation of pixels for various DEMs (DTM 5, DTM 4, DTM 3, DTED 2). \(75\%\) of the area in DTM 4 (12 ha); \(33\%\) of the area in DTM 3 (5 ha); \(20\%\) of the area in DTED 2 (3 ha). 4. Influence of other factors on the deviation of the passable area: * The better the passability conditions, the smaller the area deviation when using less accurate relief models (see Table 4); this applied to the following conditions: \(\bigcirc\) lower soil moisture; \(\bigcirc\) more suitable soil types (clayey-sandy); \(\bigcirc\) more powerful vehicles (suitable for cross-country movement). 5.