Applying Automatic Speech Recognition (ASR) in the domain
of analogue voice communication between air traffic
controllers (ATCo) and pilots has more end user requirements
than just transforming spoken words into text. It is useless,
when word recognition is perfect, as long as the semantic
interpretation is wrong. For an ATCo it is of no importance if
the words of greeting are correctly recognized. A wrong
recognition of a greeting should, however, not disturb the
correct recognition of e.g. a “descend” command. Recently, 14
European partners from Air Traffic Management (ATM)
domain have agreed on a common set of rules, i.e., an ontology
on how to annotate the speech utterance of an ATCo. This paper
first extends the ontology to pilot utterances and then compares
different ASR implementations on semantic level by
introducing command recognition, command recognition error,
and command rejection rates. The implementation used in this
paper achieves a command recognition rate better than 94% for
Prague Approach, even when WER is above 2.5
