One of the commonly used approaches, for the flow measurements in sewer systems, are velocity-area methods. Although, it is reported that the velocity sensors operate with high uncertainty, the popularity of these methods stem from the fact that they can be applied in wide range of hydraulic conditions including the mixed flow conditions. Uncertainties are related both to the applied instruments and properties of the measurement site. In order to overcome this issue, additional site-specific calibration procedure for flat EM sensors is presented in this paper. Concept of its application in the engineering practice example are presented
