VOR Multipath Error in the Presence Wind farms
Résumé
For air transport navigation, VOR systems are crucial: they give to aircraft their direction with respect to North. However, this information can be deteriorated by nearby obstacles, which yield multipaths. Signals coming from unwanted directions are processed by the on-board VOR receiver, which modify the displayed bearing. In this context, we propose and validate a method hybridizing the parabolic equation method (PE) with physical optics (PO) to compute the VOR multipath error. The modelling follows four steps. First, the field is calculated on the wind turbines using PE. One PE simulation is performed for each wind turbine. Second, the currents on the scatterers are calculated from the PE incident field. Third, the field radiated by the currents is computed on the receiver by PO. Finally, a VOR error is applied by considering the multipaths and the direct field. With this method, simulations account for a possible hilly terrain and a generic model of wind turbines that includes dielectric blades. Besides,
the output is the VOR error, which is easily interpretable for the air transport community. As an example, the case of a specific wind farm will be presented. This example will contain validations with flight inspection measurements