Feasibility Demonstration of Terrestrial RNP with LDACS Okuary Osechas 1 , Shrivathsan Narayanan 1 , Omar Garc´ ıa Crespillo 1 , Gianluca Zampieri 1 , Giuseppe Battista 2 , Rachit Kumar 3 , Nicolas Schneckenburger 4 , Elisabeth Lay 5 , Boubeker Belabbas 1 , and Michael Meurer 1 1 German Aerospace Center (DLR), Oberpfaffenhofen, Germany 2 Airbus, Ottobrunn, Germany 3 Airbus, Bengaluru, India 4 Hensoldt Sensors, Taufkirchen, Germany 5 TNG Technology Consulting, Unterf¨ ohring, Germany Abstract In this paper we discuss the first results from a set of flight experiments. The objective was to show that terrestrial ranging can support aviation services with sufficient accuracy for non-precision approach. The experi- mental setup is based on using LDACS signals to provide pseudorange measurements. The data analysis reveals that the position solutions are compliant with RNP 1 standards. We also propose the feasibility of RNP 0.3 using LDACS as terrestrial ranging. Introduction While many existing systems are capable of supporting current and near-term plans in Alternative Position, Naviga- tion, and Timing (APNT) services, it has become apparent that state-of-the-practice technologies will not support the most demanding Performance-Based Navigation (PBN) services. Specifically, to achieve the most demanding Required Navigation Performance (RNP) types, Distance Measuring Equipment (DME) will not be sufficient [1], so new methods and hardware are needed. The use of the L-Band Digital Aeronautical Communications System (LDACS) for navigation applications has long been proposed as a way of pushing the envelope on terrestrial RNP, in particular moving towards RNP 1 or RNP 0.3 types [2]. Project Alps (Alternative Positioning System) was conceived to demonstrate the feasibility of implementing RNP services on terrestrial ranging, using LDACS. The cusp of the Alps effort was a measurement campaign using dedi- cated elaborate flight trials, in the summer of 2018, which demonstrated how the navigation performance of LDACS can support RNP 1 and even RNP 0.3. This is the first time that an APNT system, based on terrestrial ranging, supports this level of performance. Motivation With increasing levels of air travel, there is increased demand for airspace capacity, which in turn increases the pressure on Air Traffic Management (ATM) systems to become more efficient. One ingredient to improve efficiency is automation, with ATM happening with less and less human intervention. The main benefit of using RNP services is, precisely, that they support aircraft movement with minimal controller involvement. This trend in automation was initially enabled by the availability of navigation services that rely on Global Naviga- tion Satellite Systems (GNSS). GNSS-based measurements support both navigation and surveillance services (e.g. ADS-B) with position estimates that have higher accuracy than any other certified system but, more importantly,