Measuring aircraft altimetry system error using automatic dependent surveillance-broadcast data / Kalyani Bahskaran

Kalyani , Bahskaran (2021) Measuring aircraft altimetry system error using automatic dependent surveillance-broadcast data / Kalyani Bahskaran. Masters thesis, Universiti Malaya.

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Abstract

The International Civil Aviation Organization (ICAO) introduced Reduced Vertical Separation Minima (RVSM) globally to support increasing traffic volumes on congested airspace. RVSM focused on reducing vertical separation minimum from 2000 feet to 1000 feet between flight level FL290 and FL410. Implementation of RVSM stresses the accuracy of aircraft avionics that report altitude and requires the Regional Monitoring Agency (RMA) to monitor the aircraft's Height Keeping Performance (HKP) to ensure the aviation safety of their airspace. Presently, air traffic and navigation are controlled by an air traffic controller on the ground based on the pressure altitude value, also known as a flight level (FL) measured with barometric altimeter. The pressure altitude was subjected to errors due to various factors including instrument defect, obstructed airflow, presence of foreign materials into the system, variations of temperature and humidity. Altimetry System Error (ASE) is the difference between the actual altitude based on SI units and the pressure altitude displayed. ASE possesses risk to the aviation industry as it is an invisible to the pilots during the flight. According to ICAO, ASE value must be less than 245 feet to ensure the safety of the aircraft. Currently, some of the airspace operators that implement RVSM in their airspace installs Height Monitoring Unit (HMU) on the ground to monitor the aircraft HKP in their airspace. However, HMU methods are disposed to drawbacks. It requires high implementation and maintenance costs, low scalability, and the requirement to have professionals on board to operate the equipment. Alternatively, this research aims to measure the ASE using geometric height data derived from Automatic Dependent Surveillance-Broadcast (ADS-B) message, which is transmitted to the Air Traffic Control (ATC) in the ground. Aircrafts in different regions has been instructed to be equipped with transponders by their authorities. Hence, the ready availability of ADS-B data can be utilized to study the HKP of the aircrafts. This research identifies a process to measure the ASE values using ADS-B data. Subsequently, a computer algorithm and interfacing tool is developed. The tool enables any personal with basic computer literacy and access to the tool and data file to process the data and asses the HKP of the flight at ease. The algorithm reads inputs of the ADS-B data file, stores all the required fields for processing either all or a single flight, and finally the ASE will be calculated. ASE value is calculated by subtracting Flight Level from the Orthometric Height of the aircraft. Orthometric height is calculated using the Geoid Height derived using the EGM96 Geopotential Model. A scatter graph is outputted displaying the FL, Datetime, and ASE values to visualize the ASE pattern and compliance throughout the flight duration. The algorithms’ accuracy is evaluated against the method adopted by China RMA comparing the Mean ASE values returned 98.84% accuracy using the same dataset. Further studies require incorporating the algorithm into the real-time Air Traffic Controller System and can be further improved with the Big Data Analytics approach in the future when it comes to processing more volume and variety of data.

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