There is growing interest in the use of semantic collections in order to identify and analyse domain knowledge. This paper describes some technical issues to consider when contemplating research which incorporates small-to-medium domain-specific word sets. The purpose of the corpus construction described was to provide an external word collection which could be transformed to a numeric frequency scale which could take the place of an "expert" in order to evaluate the lexical content of aircraft Visual Landing Approach concept maps. Although this paper is based on research in the field of aviation education, the underlying principles are more widely applicable. (Contains 3 tables and 4 figures.)