Data quality, concepts and methodology: Data quality and limitations

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Aircraft movement statistics are accumulated from data originating with air traffic control tower units or flight service station personnel. Because staff in these positions are highly trained in factual observation and reporting, the entries in the data bank are of a high quality.

The procedures for reporting aircraft movements on the Daily air traffic records by tower units are described in the NAV CANADA Air traffic control manual of operations (TP 703) Volume 1, Para. 1023 to 1023.5. Definitions for terms used in these paragraphs can be found in the appendix II "Glossary of terms" of this report.

To maintain uniformity in the reporting of source data, ASC issues to air traffic control units an "Air traffic designators" handbook (TP 143) listing the official Transport Canada aircraft type designators and the designators of various domestic and international air carriers. This handbook and another titled "Canada flight supplement" listing various airport codes serve as references to help ensure the reporting of the proper aircraft identity and the point of origin and destination of flights.

The processing system contains editing procedures designed to identify data errors occurring during transcription or during data capture of forms. Identified errors are manually corrected by ASC editing staff.

Errors may occur if an aircraft type code which exists is reported or data captured in error for a flight. For example, the reporting or keying of B727 for a flight actually performed by a B737 may not be detected during the system editing. That the aircraft type information is recorded by highly trained air traffic control tower staff using a common handbook of official aircraft codes will minimize this problem.

Similarly, the breakdown of the data on a geographic basis by use of location codes can be subject to error. For smaller locations, alphanumeric location codes are often used and the sequence of numbers and letters determines the geographic area to which the data are assigned. In some cases, where a sequence error has been introduced into the system either at the reporting unit or at data capture, a domestic movement may be classified as transborder or vice versa. The use of common manuals of location identifiers works to minimize this occurrence.