"The objective of the project is to develop a high fidelity and accuracy GPS system simulation, capable of being seemly integrated in Green Regional Aircraft (GRA) flight simulator.The development of a green FMS is an essential factor for integrating green technologies in GRA simulator and for achieving the following Clean Sky environmental goals.• 50% reduction of CO2 emissions• 80% reduction of NOx (nitrogen oxide) emissions• 50% reduction of external noiseTo support the green FMS system development, a GPS simulator shall be developed taking into consideration that navigation scenarios presented by both NextGen (EUA) and SESAR (UE) Master Plans.These Roadmaps present the FMS increasingly relying on GNSS systems, in particular the current SESAR 2020 Navigation roadmap considers the following scenario:• Primary aircraft positioning means will be satellite based for all flight phases;• Positioning is expected to rely on a minimum of two dual frequency satellite constellations (Galileo, GPS L1/L5 and potentially other constellations, assuming interoperability) and augmentation as required:• Aircraft based augmentation (ABAS) such as INS and multiple GNSS processing receiver;• Satellite based augmentation (SBAS) such as EGNOS and WAAS.And Beyond 2020 :• The availability of other constellations enables increased accuracy and availability. Multi constellation receivers are able to exploit available constellations/satellites (e.g. China, Russia),• Ground based augmentation (GBAS) for Cat II/III approach and landing with backup provided by ILS/MLSAs part of this project a simulator infrastructure shall be implemented with a modular architecture that can be further extended to cope environment presented above and that shall provide a realistic GPS simulation infrastructure. Being this high level of realism achieved through the use of EGNOS data for the validation and fine tuning of the several GNSS signals errors sources contributions."