[en] Following the Chernobyl accident in 1986, diverse sampling and measurement methods for radioactivity deposition have been applied by the various European institutes. When compiling these datasets together on the same data platform, in view of preparing the atlas on cesium contamination in Europe, data quality analysis has shown a lack of harmonisation between these various methods. Because of the necessity to dispose of compatible and representative measurements for further analysis, e.g. time series analysis, and the need for better Standardization methods in the event of a future accident with large transboundary release, several suggestions are made of how such harmonization might be achieved. Also in view of taking appropriate decisions in case of accidental releases by gaining experience in data Standardization, the variety of the sampling and measurement methods of radioactivity currently used are briefly summarized and the results intercompared. In order to improve the quality of datasets, GIS, amongst other methods, can be applied as a useful tool to highlight the lack of harmonisation between the various sampling methodologies by indicating the data uncertainty