In the data warehouse (DWH), all measurement data are consolidated in order for them to be stored over the long term in a standardised form. Once stored in the DWH, the data then undergo various preparation processes. The older the measurement data, the more calculations, quality assurance checks and amendments that have been performed. Not all data series are subjected to the complete preparation process. Rather, the exact processing programme depends on how the data will be used. The most important processing steps include calculating additional parameters, filling measurement gaps and making corrections.