Distance Determination Between WGS84 Coordinates: An Assessment of Approximation Methods for Reduced Computational Complexity

Due to the enormous fields of application, Unmanned Air Systems (UAS) nowadays differ inter alia in size, weight, thrust and range. The high diversity of application imposes a broad range of requirements to the flight control software of the Unmanned Air Vehicle in terms of complexity, computational effort and tracking performance. Trajectory flights based on way-points, automatic take-off and landing capabilities, or safe area detection and adherence algorithms require reliable and accurate distance and flight path calculation methodologies. This paper reviews, analyses and evaluates seven different methods to calculate the shortest distance and its corresponding flight path course between coordinates on the WGS84 reference ellipsoid. Depending on the operating distance of the UAS, the accuracy and the computational complexity can be reduced dramatically by utilizing an application-adapted calculation method. This paper recommends the suitable approximation method for the application of your Unmanned Air Vehicle System. Since the computational complexity gets rising significance due to software verification and safety assessment the distance calculation should be kept as simple as feasible by utilizing the appropriate distance calculation method while maintaining accuracy and tracking performance. The feasibility of the proposed methods is discussed for three different typical application scenarios.