Enhanced Approach Procedures Based on OAS Constraints and BDSBAS Performance Evaluation

Traditional Instrument Landing Systems (ILSs) suffer from inherent limitations, including limited signal coverage and high maintenance costs. To address these issues, we propose a novel approach procedure design method based on the BeiDou Satellite-Based Augmentation System (BDSBAS), which is particularly suitable for airports with complex terrain conditions or no ground-based navigation infrastructure. In this method, a geometric constraint model of the approach trajectory is constructed in a local Cartesian coordinate system, and obstacle clearance performance is evaluated based on the Obstacle Assessment Surface (OAS) theory. Global Navigation Satellite System (GNSS) observations and BDSBAS augmentation data are processed collaboratively to calculate aircraft position solutions, as well as the corresponding horizontal and vertical protection levels, enabling comprehensive evaluation of the navigation system’s accuracy, integrity, continuity, and availability. The feasibility and performance of the proposed method are verified through practical airport deployment and dynamic flight tests. Experimental results show that the 95th-percentile horizontal and vertical position errors reach 1.31 m and 4.17 m, respectively, and all valid observation epochs fully comply with the protection level and alert limit specifications. Compared with the conventional ILS-based scheme, the proposed method reduces the total OAS area and the missed-approach Z-surface area by 44.25% and 67.90%, respectively. The findings demonstrate that BDSBAS can effectively support approach procedure design and guarantee high-precision navigation performance, while significantly reducing the reliance on airport-specific ground navigation infrastructure.