Increasingly popular cognitive mapping of ill-structured socio-economic, manufacturing and other systems and situations carries risks for validity of end results. The problem of validity of expert estimates on prescribed normalized universal scales is raised. The main factor of risk is supposed to be the conceptual vagueness of expert knowledge on ill-structured systems and situations and knowledge of theoretical models for their cognitive mapping. An approach to analysis of expert estimation validity of variable values in cognitive mapping is proposed. In the approach the model of conceptual interpretation of a prescribed universal scale for an estimated variable is proposed. The model of conceptual interpretation enables to refine the influence of conceptual vagueness onto the expert estimation validity. Some results of empirical testing of the proposed approach operability in cognitive mapping are presented.