Enabling LAAS airport surface movement: mitigating the anomalous ionospheric threat

The Local Area Augmentation System (LAAS) can be used for both precision approach and Differentially Corrected Positioning Service (DCPS) applications. Through its support of DCPS, the LAAS Ground Facility (LGF) is required to meet the integrity requirements of all other operations that could use the LAAS VHF Data Broadcast (VDB). Our previous work [1,2,3] demonstrated that the existing DCPS integrity requirements cannot be met by CAT I LAAS without changes to both the definition of DCPS integrity [4,5] and the airborne receiver requirements [6]. One of the implications is that some future applications of LAAS that planned to use DCPS, such as airport surface movement, cannot be supported by DCPS with the CAT I LAAS architecture. However, if airport surface movement is defined as a separate operation, it could be supported by the existing LGF geometry screening that mitigates the anomalous ionospheric threat for CAT I precision approach. The only change needed would be to increase σpr_air in airborne equipment to bound the higher multipath errors in the airport surface environment. Confirming this hypothesis requires a more-intensive study of the requirements of airport surface movement and is the subject of this paper. If LGF geometry screening itself cannot support airport surface movement, the results in this paper include additional aircraft geometry screening proposed in [2] to lower the Maximum Acceptable Error (MAE) to a usable level while maintaining useful availability.