Initial Trajectory Sharing – DIGITS

Exploring techniques for efficiently collecting trajectory data

Initial Trajectory Sharing, project DIGITS, is a SESAR joint undertaking project which has completed research and demonstrated, through a large-scale trial, that it is possible to downlink data from aircraft upon request from the ground.

Up till now, when we’ve wanted information about an aircraft’s trajectory we’ve used predicted data which has come from ground based systems, and while it’s reliable it doesn’t always match the actual behaviour and intent of the aircraft.

The data collected from the aircraft as part of this trial has allowed for trajectory information from the aircraft’s flight management system to be downlinked in real time, collected and used in planning and decision-making, as well as demonstrating the potential for optimising trajectory-based operations.

This capability, known as Automatic Dependent Surveillance - Contract (ADS-C), can be used for surveillance and route monitoring, allowing us to predict speeds during different flight phases, and estimate times and altitudes for the various waypoints along the route of an aircraft.

As one of the ANSP project partners, we contributed by running validation exercises, analysis using various data sets and demonstrations in the ops room, reporting on our research findings from this large-scale demonstrator trial.

Our contribution to this project involved setting up a demonstrator as part of an initial exercise in the Prestwick Ops room to show the benefit of using ADS-C data.  Our team used simulated data and traffic samples to show controllers how ADS-C data can be used on their workstations and explored several use cases on how the trajectory information can support conflict detection.  This exercise was very successful, with about 50 operational colleagues from different Watches actively participating.

Once aircraft started to be equipped as part of the large scale trial, the ground based systems set up ADS-C with an aircraft. Various data were requested and downlinked from the aircraft including the Extended Projected Profile (EPP) data – essentially the aircraft’s trajectory – from its flight management system. This allowed us, as part of the second phase of this project, to explore the feasibility of using trajectory information from the aircraft to complement the knowledge and capability currently available in just the ground-based systems and tools.

The project trial used ADS-C data collected from 91 aircraft from multiple airlines, operating in major European airports, which were upgraded with avionics capable of sharing ADS-C data. This was known as the ‘DIGITS fleet’ and has been in operation since April 2019.

Data gathered from this fleet between April 2019 and February 2020 was used to complete the research and data analysis by the NATS R&D team, with the results demonstrating that ADS-C supports a better harmonisation between aircraft intent and the ground-based trajectory prediction. The project has shown promising results in terms of predicting time of arrival to waypoints. With that said, a wider assessment of the usability of ADS-C needs to be undertaken to better understand the extent of the support ADS-C can provide to ATM operations.

This project has paved the way for further projects and solutions that are continuing to study the potential support ADS-C can provide to ground systems, including follow-on projects within the SESAR Joint Undertaking collaboration.

The PJ31 DIGITS and DIGITS-AU projects that have received funding from the SESAR Joint Undertaking under grant agreement No 731818 and complementary grant agreement No 783178 under European Union’s Horizon 2020 research and innovation programme. The abbreviation DIGITS/-AU is used when reference is made to both projects as a whole.

Potential benefits

Cost savings

Reduced workload

Increased capacity

Trajectory prediction

Improved environment

Increased fuel savings

Increased punctuality

Enhanced safety

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