# The Influence of the Quality of Digital Elevation Data on the Modelling of Terrain Vehicle Movement
## 3 Results
### Efficiency Improvements of the Elevation Models

Table 6: The comparison of the extent of passable, hardly passable, and impassable areas with different elevation models (DTM 5, DTM 4, DTM 3, DTED 2) without slope corrections and with slope corrections. Location: Kdynne, 6 km \(\times\) 6 km, moist conditions, GO max slope = 10\({}^{\circ}\), SLOW GO max slope = 20\({}^{\circ}\). The main improvements in the results are displayed as bold values. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**GO or SLOW GO** & \multicolumn{3}{c}{**Reduced Slope Values (\({}^{\circ}\))**} \\ \cline{2-4}
**Slope Value (\({}^{\circ}\))** & **DTM 4** & **DTM 3** & **DTED 2** \\ \hline
35 & 32.0 & 29.0 & 27.0 \\
40 & 36.0 & 32.8 & 30.5 \\
45 & 40.0 & 36.5 & 34.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._ \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **DTM 5** & **DTM 4** & **DTM 3** & **DTED 2** \\  & & **Area (\%)** & **Area (\%)** & **Area (\%)** \\ \hline \multirow{3}{*}{No slope corrections} & GO & 43.67 & 44.25 & 43.77 & 43.72 \\  & SLOW GO & 36.36 & 37.37 & 40.79 & 42.53 \\  & NO GO & 19.97 & **18.38** & **15.44** & **13.76** \\ \hline \multirow{3}{*}{With slope corrections} & GO & 43.67 & 43.61 & 41.12 & 38.89 \\  & SLOW GO & 36.36 & 35.49 & 35.16 & 37.03 \\ \cline{1-1}  & NO GO & 19.97 & **20.90** & **23.72** & **24.08** \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The comparison of the extent of passable, hardly passable, and impassable areas with different elevation models without slope corrections and with slope corrections. Location: Dolni Morava, 3 km \(\times\) 3 km, moist conditions, GO max slope = 10\({}^{\circ}\), SLOW GO max slope = 20\({}^{\circ}\). The main improvements in the results are displayed as bold values. Figure 9: The map comparison of the CCM analysis with different elevation models (DTM 5, DTM 4, DTM 3, DTED 2) without slope corrections and with slope corrections. The slope corrections enabled accurate results of CCM analysis for lower-detail models. DTM 5 (1 m \(\times\) 1 m) served as the reference model. Figure 10: A map comparison of the CCM analysis with different elevation models (DTM 5, DTM 4, DTM 3, DTED 2) without slope corrections and with slope corrections. The slope corrections enabled more accurate results of CCM analysis for lower-detailed models. DTM 5 (1 m \(\times\) 1 m) served as the reference model Choosing a larger area (6 km \(\times\) 6 km) confirmed the correctness of the slope-reduction method. The accuracy of the selected method of slope corrections could be observed from an extent of impassable terrain calculated from the selected elevation models. The impassable area was significantly more accurate with implemented slope corrections. More important is the fact that these slope adjustments allowed for distinguishing hardly passable and impassable terrain with noticeably higher precision. On the right side of the map (Figure 9) is a valley that represents an impassable obstacle. Without corrections, the valley was evaluated as hardly passable when using DTM 3 and DTED 2. With implemented corrections, the valley was correctly displayed as impassable also in these lower detail models. Furthermore, shapes of other major terrain features representing hardly passable terrain were displayed more accurately (e.g., a small valley in the lower-left corner of the map). The detail of DTM 5 allowed for displaying a fragmented terrain (e.g., top left corner). These locations are usually joined as one area in lower detail models, especially with details that were 10 m \(\times\) 10 m and above. This was the reason for the higher ratio of impassable terrain with corrected slopes. Due to the fragmented terrain, the mentioned location was, in the end, completely impassable. This meant that the lower-detailed models were displaying the correct situation. The results in Figure 9 were confirmed in Figure 10 for a different location. The extent of the impassable area is given with the corrections adjusted to a more real coverage and position.