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Supporting the Aircraft Access to System Wide Information Management through Data Compression
238 Seiten, Dissertation Technische Universität Darmstadt (2018), Softcover, A5
The number of aircraft movements rises almost every year, which poses a huge challenge for the Air Traffic Management (ATM) system. Therefore, to accommodate this rising demand for air traffic, a number of improvement concepts have been developed. System Wide Information Management (SWIM) is one of those and it is considered a key enabler for many optimisations of the future ATM system, both on the ground and in the air.
This thesis identifies a gap in the vision of having the aircraft as a mobile SWIM node. The size of SWIM messages is way bigger than the size of data link messages exchanged today and still too big for exchanging those over future data links.
For the purpose of this thesis, the focus is on Digital NOTAM (D-NOTAM) messages that are essential for the safe operation of all aircraft. The sample data, encoded in the Aeronautical Information Exchange Model (AIXM) 5 format, is made available by the European Organisation for the Safety of Air Navigation (Eurocontrol) from two of the D-NOTAM trial campaigns between 2008–2010 and presents a realistic sample of SWIM messages. A detailed analysis of this data identifies many deficiencies from a message-size point of view and a number of possible optimisations. Most of these optimisations are generic and can be applied to any Extensible Markup Language (XML) data. Some are specific to Geography Markup Language (GML) encodings, and one is applicable only to the D-NOTAM data. Nevertheless, even with these optimisations the required message-size reduction could not be achieved.
Therefore a new, modular compression algorithm is developed, which is based the on Efficient XML Interchange (EXI) specification. The test results prove which combinations of compression optimisations applied to the core algorithm, provide the best results on the D-NOTAM data. Many of the proposed compression optimisations are applicable to any XML data and some are specifically designed for geospatial values encoded in GML. This makes the algorithm particularly interesting for aeronautical and meteorological SWIM data encoded in the AIXM 5 format and the ICAO Meteorological Information Exchange Model (IWXXM) format.
The final results on the D-NOTAM data prove that using data compression SWIM messages can be exchanged over a multitude of different data links. It is also shown how the proposed data compression nicely fits in the overall vision for the future ATM system.