The geo base data at the heart of the IOER Monitor is updated by the surveying agencies of the individual states in a regular three- or five-year cycle. Monitor indicators are calculated annually (from 2013) in order to provide the most up-to-date information on land use. Furthermore, the aim is to determine selected indicators on the basis of analogue topographic maps from earlier time frames in order to offer long-term monitoring of successive periods.
In the indicator tables it is only possible to compare current values with those of previous time frames. The shown differential, however, is calculated in the direction of development (from old to new).