IWAC2022 Program & Abstracts
Day 2 (Wednesday, 26 October) 9:30 - 11:00, Hall C

Technical Session 3Global Navigation Satellite Systems

T3-1-A
Identification and Operational Impact Analysis of GNSS RFI Based on Flight Crew Reports andADS-B Data
Patric Fol, Michael Felux (Zurich University of Applied Sciences)

Today, satellite navigation is the primary means of navigation in civil aviation. Global Navigation Satellite Systems
offer global coverage, high accuracy, and reliable position information. They are not only used for en-route navigation
but there are also approach procedures based on satellite navigation and safety systems like the Terrain Avoidanceand Warning System, that depend on its reliable data. However, Global Navigation Satellite Systems also have theirweaknesses; as the signals from space are very weak, they can easily be disturbed. In recent years, reports about socalled radio frequency interference strongly increased which poses a problem for civil aviation. Airlines have identified
the risks associated with radio frequency interference but data on such events is scarce. This paper analyzes AutomaticDependent Surveillance-Broadcast data of flights where cockpit crews reported issues that are in line with the expected
effects of radio frequency interference. The analysis showed that the effects of radio frequency interference are clearlyvisible in the Automatic Dependent Surveillance-Broadcast messages, which therefore can serve as a useful source of
information to get a holistic picture about the extent of radio frequency interference. Together with flight crew reports
describing the effects in the cockpit for different aircraft types, the operational impact of such jamming events can thenbe assessed.

T3-2-A
Impact of GNSS Outage on Mid-Air Collision Risk

Benoit Figuet, Manuel Waltert, Raphael Monstein, Felux Michael (Zurich University of Applied Sciences)
Automatic dependent surveillance broadcast technology is transforming aviation by providing air traffic controllers with
fast and accurate surveillance capabilities which rely on aircraft broadcasting their position obtained typically throughthe global navigation satellite system. While satellite navigation enables accurate positioning, it remains vulnerable toexternal disturbances, which can be triggered by multiple causes, such as intentional jamming or ionospheric events.
In such cases, navigation systems revert to less accurate navigation techniques, such as inertial sensors or groundbased radio navigation aids. This study comes with two main objectives: (i) to study the impact of an outage of satellite
navigation systems on mid-air collision risk due to navigation performance degradation, and (ii) to translate collision
probabilities due to navigation error into minimum spacing requirements. In this context, this study simulates navigation
errors of real world trajectories by using a probabilistic radio navigation error model. Results show that the risk of midair collisions is increased in case of a degradation of the navigation performance. However, it stays well below thetarget level of safety when ground-based navigation aids are used instead of satellite navigation.

T3-3-A
Preliminary Evaluations of User Positioning Errors in DFMC SBAS Demo at Thailand Location

Somkit Sophan, Lin M. M. Myint, Pornchai Supnithi (King Mongkut’s Institute of Technology Ladkrabang)
Satellite-based augmentation system (SBAS) is an integral part of modern-day aeronautical navigation. Recently, thedual-frequency multi-constellation (DFMC) SBAS based on the L1 and L5 frequencies (1575.42 MHz and 1176.45 MHz)
have received a wide attention. However, the ionosphere-free combination (IF) technique used in DFMC SBAS brings
about relatively higher noise levels compared with the L1 frequency-only approach. Importantly, the suitable radius(distance) between the user and reference receivers needs to be investigated for the preliminary SBAS corrections
and performances. Therefore, in this work, we investigate the long-term correction (LTC) parameters generated fromthree reference stations in Thailand. The positioning performances of DFMC SBAS demo (GPS and Galileo satellites)
are investigated. The positioning results are calculated based on the single point positioning (SPP) algorithm. Using theestimated LTC parameter (radius of ~587 km) on quiet days, the positioning errors in horizontal and vertical directions
are 1.38 and 2.59 m, respectively. In addition, on disturbed days, the horizontal and vertical errors are 1.50 and 2.93 m,respectively. From the study, the reference stations in the radius of ~600 km can be considered a suitable range for theDFMC SBAS demo at Thailand location.

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