C3 in UAS as a Means for Secondary Navigation Jorge Ramirez, Dagoberto Salazar, Xavier Prats and Cristina Barrado (Castelldefels School of Telecommunication and Aerospace Engineering, Technical University of Catalonia, Barcelona, Spain) (E-mail: joraalc@gmail.com) Unmanned Air Systems (UAS) navigate using Global Navigation Satellite Systems (GNSS), but GNSS vulnerability precludes its use as the only means of navigation and requires a secondary means of navigation. A differentiating characteristic of UAS is their periodic communications with the ground station. This paper analyses the adequacy of employing UAS Command, Control and Communications (C3) as a secondary means of navigation. With no additional infrastructure, an Extended Kalman Filter (EKF) is used to process C3 messages and to obtain the positions of the UAS. Navigation accuracy and integrity are calculated in a scenario with three UAS. The obtained results meet the International Civil Aviation Organization (ICAO) Performance-Based Navigation (PBN) requirements. KEY WORDS 1. UAS. 2. Relative Navigation. 3. C3. 4. Secondary Navigation Means. Submitted: 14 March 2012. Accepted: 28 June 2012. First published online: 29 August 2012. 1. INTRODUCTION. The large number of navigation systems in today’s aircraft have motivated studies regarding the integration and fusion of various legacy navigation sources, where different architectures providing fault tolerance are evaluated (e.g., Baraniello and Corraro, 2010). The MITRE Corporation Center for Advanced Aviation System Development presents results from a human-in-the- loop study of cockpit display of traffic information enabled delegated separation, which is based on the availability in the cockpit of the surrounding traffic information (Domino et al., 2010). Table 1 summarises the accuracies in nautical miles (NM) required by ICAO in the latest version of the Performance-Based Navigation (PBN) Manual (ICAO, 2008). The initial 4 rows (RNAV 10 to RNAV 1) correspond to the accuracies of RNAV (a Rea NAVigation) in which the less restrictive value corresponds to the operations over oceanic areas (10 NM). The values of 5 NM and 2 NM are the accuracies that are applicable to the continental and arrival phases, respectively, and the more restrictive accuracy (1 NM) is also applicable to several phases in the approach. The last 3 rows of Table 1 are the accuracies required to perform operations in Required Navigation Performance (RNP). The main difference between RNAV and THE JOURNAL OF NAVIGATION (2013), 66, 115–134. © The Royal Institute of Navigation 2012 doi:10.1017/S0373463312000392 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0373463312000392 Downloaded from https://www.cambridge.org/core. IP address: 3.235.21.12, on 23 May 2020 at 23:47:58, subject to the Cambridge Core terms of use, available at