Some selected parameters of the ILS measurements which can be particularly challenging are localizer alignment and structure, and glide path angle and threshold crossing height (TCH). This paper describes these challenges, citing both European and United States (US) experiences and views, with specific examples and data. It discusses the technical issues involved, and makes recommendations for measurement methods (e.g. data filters, sensor antennas), mathematical treatments of data (e.g. averaging and weighting schemes), and process standardization. Results of alternative measurement setups gained by simulations will be presented for the clarification of the technical problems and for support of the proposals.