Proposal of UAS Strategic Conflict Detection Concept with a Centralised Service in Multi-USSP Environment Using an Octree Data Structure

U-space regulation require the use of specific U-space services (USSs) to ensure safe UAS operations within the so-called U-space airspaces. One of the key services is the Flight Authorisation Service (FAS). The FAS is responsible for granting authorisation for UAS flights by reviewing flight authorisation requests (FARs), also known as U-plans. To obtain acceptance of the request, an efficient strategic conflict detection is needed. This paper presents an approach to detect strategic conflicts in U-space airspaces in multi USSP environments, facilitating the resolution of potential conflicts between UAS 4D trajectories included in the U-plans submitted to the FAS. The proposal is based on regulatory requirements and inspired by the discretised airspace set out in ASTM F3548-21. The services developed in this proposal encompass the Flight Authorisation Service, as defined in the U-space regulation, and two additional services: the U-Plan Preparation Service (UPPS) and the Search For Overlap Service (SFOS). The UPPS assists operators in creating their U-plan by defining the intended trajectory waypoints and is responsible for the creation of realistic 4D operational intents considering flight uncertainties by using the PX4 autopilot software-in-the-loop (SITL) environment with gazebo as the simulation platform. The SFOS implements an octree data structure to build and manage in an efficient way the airspace representation used by ASTM F3548-21 to enable the operation of multiple USSPs in the same U-space airspace. The proposed solution has been evaluated through simulations with varying level of UAS traffic density as well as different trajectory types (linear and area-based). The results demonstrate the algorithm's ability to detect conflicts and the time required for detection in different density scenarios, and show the impact of the area-based trajectories.