Construction and Capacity Evaluation of Urban Low-Altitude Reachable Airspace

With the rapid development of drone technology, urban low-altitude airspace, as a key area for drone flights, is facing unprecedented traffic pressure. In urban environments with high-density building distributions, the evaluation of low-altitude airspace capacity becomes particularly important. This paper proposes a new method for evaluating low-altitude airspace capacity, and establishes a more accurate airspace capacity assessment model by considering building distribution and drone avoidance strategies. By introducing the visibility analysis method from spatial syntax theory, a conflict detection model based on the minimum restricted visibility area is constructed, and the collision risks between drones and buildings, as well as between drones, are quantitatively assessed. Simulation results show that as the number of drones increases, the number of collisions per flight hour grows exponentially, while low-altitude airspace capacity remains insensitive to changes in collision probability thresholds. Further analysis reveals that as the flight altitude increases, airspace capacity rises significantly, particularly at altitudes of 30, 50, and 70 m, where a sharp change in capacity is observed. This finding provides theoretical support for the selection of low-altitude flight layers and airspace management.