# Method to Characterize Potential UAS Encounters Using Open Source Data
## 4 Discussion
### Geography  
The long linear infrastructures of railways, major roads, pipelines, and electric power lines are often no more than a few nautical miles apart. These features are not uniformly distributed across the environment, rather geographical features of mountains and lakes influence the location and man-made features. This is exemplified by Figure 4 for geographical and man-made features around the White Mountains National Forest. Foremost, the long linear infrastructure traverses through the natural mountain pass south of Franconia Notch near Woodstock. It is more efficient to build power lines and roads through valleys instead of steep and varied mountainous terrain. The mountain pass acts as a natural constraint on the location of the manmade features. The electric power lines to the west of the mountains were likely constructed there to minimize costly construction and maintenance due to challenging terrain. A different constraint is Lake Winnipesaukee to the south of the mountains, there are no long linear infrastructure features traversing through it. Instead the railway and roads border the western edge of \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Feature \#1** & **Feature \#2** & **Total Point Pairs** & **Compute Time (s)** & **Mean (nm)** & **Median (nm)** \\ \hline FAA Obstacles & Golf Course & 1754\% & 2113\% & 4.2\% & 6.1\% \\ FAA Obstacles & Pipeline & 1797\% & 2210\% & 4.0\% & 1.0\% \\ FAA Obstacles & Railway & 1455\% & 2623\% & 1.0\% & 4.4\% \\ FAA Obstacles & Road & 1800\% & 2705\% & 3.3\% & 7.3\% \\ FAA Obstacles & Wind Turbine & 282\% & 2442\% & -3.8\% & \(-4.9\%\) \\ Electric Power & FAA Obstacles & 1791\% & 356\% & 0.3\% & 0.6\% \\ Electric Power & Golf Course & 2303\% & 1681\% & 0.3\% & 0.6\% \\ Electric Power & Pipeline & 2359\% & 1826\% & 0.2\% & 0.4\% \\ Electric Power & Railway & 1916\% & 2001\% & 0.4\% & 0.8\% \\ Electric Power & Road & 2363\% & 190\% & 0.3\% & 0.6\% \\ Electric Power & Wind Turbine & 395\% & 280\% & 0.1\% & 0.1\% \\ Golf Course & Pipeline & 2311\% & 2179\% & \(-0.3\%\) & \(-0.2\%\) \\ Golf Course & Railway & 1876\% & 2699\% & 0.1\% & 0.4\% \\ Golf Course & Road & 2315\% & 2383\% & 0.1\% & 0.3\% \\ Golf Course & Wind Turbine & 385\% & 389\% & 0.0\% & \(-0.1\%\) \\ Pipeline & Railway & 1922\% & 2712\% & 0.2\% & 0.2\% \\ Pipeline & Road & 2371\% & 2461\% & 0.2\% & 0.2\% \\ Pipeline & Wind Turbine & 397\% & 346\% & 0.1\% & 0.2\% \\ Railway & Road & 1925\% & 2057\% & 3.9\% & 3.4\% \\ Railway & Wind Turbine & 307\% & 338\% & 0.4\% & -0.3\% \\ Road & Wind Turbine & 397\% & 388\% & 0.0\% & 0.0\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Percent differences for US-CA results when changing spacing from 500 to 100 feet. the lake. For potential UAS operations, this geography will likely increase or decrease the likelihood that two UAS will encounter each other. Nevertheless, as illustrated by Figure 5, geographical features are not solely responsible for influencing the location of man-made features. The environment in Figure 5 is relatively flat and consistent, yet the long linear infrastructures are within 0.5 nautical mile or less of each other. These features align with U.S. Route 2 which was built in 1926, followed by the Great Northern Railway (the eventual Amtrak \"Empire Builder\") route in 1929. There are engineering design standards to reduce the environmental impact of new transportation routes by locating railway tracks alongside a highway. The nearby transportation system minimizes environmental impact by jointly using land while also increasing the efficiency of multi-vehicle trips. Additionally, Figure 5 illustrates that specific features, such as wind turbines, are located at specific locations to optimize their operations. The wind turbines are located to maximize energy production while minimizing environmental costs. UAS operations could leverage this when designing risk mitigations.