Fixed administrative boundaries of defined administrative units are of fundamental importance for spatial analysis. In the Monitor of Settlement and Open Space Development, indicator values are basically determined on the basis of such administrative units (municipalities, districts and independent cities, federal states). The ATKIS Basis landscape model, which is the most important source of data for the IOER Monitor, requires suitable geometric administrative areas at scale 1:25,000 for GIS analysis.
In view of the ongoing reform of administrative boundaries in Germany, an annual updating of the geometry of administrative boundaries with clearly designated municipalities is required by 31 December. Due to the lack of nationally available geo base data up to the year 2012, ATKIS data is processed as required by the IOER (for methodology see Schumacher; Krüger; Kaden 2013: Revisions of Government and Administrative Boundaries: Towards the Creation of an Administrative Boundary Geometry VG25 from the ATKIS Basic Landscape Model. In: Kartographische Nachrichten 63(2013)5, 276-282).
The Federal Agency for Cartography and Geodesy (BKG) has supplied national geo base data in the form of Verwaltungsgebiete VG25 from 31.12.2013. This data is now used by the IOER Monitor. Each updated version of VG25 is derived afresh from the Basis DLM, which includes all corrections to boundaries as provided by the state survey authorities. Therefore, minor geometric disparities in the boundaries of administrative units over various timeframes may appear even if there have been no changes in the actual administrative area.