# Airspace Geofencing and Flight Planning for Low-Altitude, Urban, Small Unmanned Aircraft Systems
## 7 Case Study with sUAS Route Deconfiction  
The above results describe single geofenced sUAS routes through a complex urban landscape. In general, UTM will manage multiple sUAS in shared airspace. This section presents a case study illustrating how the proposed geofencing pipeline supports multiple-sUAS deconfiction. For this study, we assume airspace is allocated first-come-first-served. Suppose \(sUAS_{1}\) and \(sUAS_{2}\) request flight plans each defined by departure and destination coordinates (WGS 84/UTM zone 18N), cruise speed, and targeted cruise altitude as defined in Table 9. Further, suppose \(sUAS_{1}\) receives approval for its flight plan and associated geofence volume before \(sUAS_{2}\) contacts UTM. \(sUAS_{2}\) will then need to plan a flight that avoids the Manhattan terrain and building geofences as well as the flight trajectory geofence wrapping the \(sUAS_{1}\) route. Figure 19 shows the resulting flight plans for \(sUAS_{2}\) as a top-down route view comparing our airspace volumization and flight corridor solutions. For this example, altitude vs. time plots for the \(sUAS_{2}\) solutions are shown in Figure 20.  
Figure 19: Top-down view of \(sUAS_{2}\) sample solutions. Five flight trajectory solutions are generated for \(sUAS_{2}\). Each solution provides route deconfiction from Manhattan terrain and building geofences and from the \(sUAS_{1}\) flight trajectory geofence. Distances traveled are 2008 m (turn), 1585 m (constant cruise), 1634 (terrain follower), 1983 (150 m flight corridor), and 2395 (500 m flight corridor). The minimum-cost solution for \(sUAS_{2}\) is the constant cruise altitude option.  
Since \(sUAS_{1}\) and \(sUAS_{2}\) have the same target cruise altitude, a maneuver was required for \(sUAS_{2}\) to deconflict its \"turn\" route from the \(sUAS_{1}\) flight trajectory, making this the longest distance solution option. On the other hand, the \"constant cruise altitude\" and \"terrain follower\" solutions were not influenced by the \(sUAS_{1}\) trajectory because the minimum building height along the straight line path from departure to destination for \(sUAS_{2}\) was greater than \(sUAS_{1}\)'s target cruise altitude. If building height placed \(sUAS_{2}\) at \(sUAS_{1}\)'s cruise altitude, \(sUAS_{2}\) would also need to climb over the \(sUAS_{1}\) geofence. Note that if \(sUAS_{1}\)'s airspace volume reservation duration was minimized using SDG or MDG, \(sUAS_{2}\)'s path had a lower probability of being impacted. Example 3-D \(sUAS_{2}\) in \"turn\", \"constant cruise altitude\", \"terrain follower\" solutions are shown in Figures 21-23.  
Figure 21: Example of a 3-D geofence wrapping a “turn” flight plan for \(sUAS_{2}\). The \(sUAS_{2}\) trajectory is shown in black, and the \(sUAS_{1}\) trajectory is shown in blue. Polyhedra (green) denote keep-out geofences around buildings. The remaining 2-D polygons denote keep-out geofences around buildings that are outside the combined ROI.  
Figure 20: Flight altitude time histories for airspace volumization and flight corridor solutions for \(sUAS_{2}\) in Figure 19 example.  
\begin{table}
\begin{tabular}{c c c c} \hline \(\mathbf{P}_{Departure}\) (**m**) & \(\mathbf{P}_{Destination}\) (**m**) & \(\mathbf{V}_{UAS}\) (**m/s**) & \(\mathbf{h}_{targetCruise}\) (**m**) \\ \hline \(sUAS_{1}\) & [584,085; 4,508,093; 0] & [584,248; 4,506,598; 0] & 30 & 50 \\ \hline \(sUAS_{2}\) & [583,600; 4,507,000; 0] & [584,460; 4,507,660; 0] & 20 & 50 \\ \hline \end{tabular}
\end{table}
Table 9: Flight plan parameters for \(sUAS_{1}\) and \(sUAS_{2}\).