The third Urban Audit exercise was launched in 2006. The collected data is referenced to 2004. It is managed by the Directorate General for Regional Policy in collaboration with EUROSTAT. The URAU_2004 polygonal geometry for UA Cities, UA City Kernels and Large Urban Zones was derived from the GISCO Communes 2004 regional feature class. Information assigning membership of each EBM 2004 commune to each of the 3 UA conceptual levels was provided at the Country level. The URAU_2004 polygonal geometry for Sub City Districts was either derived from the GISCO Communes 2004 regional feature class (where information assigning membership of each EBM 2004 commune to hierarchical sublevels levels was provided at the Country level), or derived from geometry supplied by URAU delegates which was made coincident with UA City geometry. Generalised versions were created for display at a scale of 1:3 Million. The point geometry of the Urban Audit Cities was based on the GISCO STTL_V3 dataset of European Settlements. Points were created in 17 cases where a UA City could not be matched to a Settlement in GISCO STTL_V3 dataset.

Creation of City, Kernel and LUZ feature classes: Country files listing UA status (City, Kernel and LUZ codes) of each EBM 2004 commune were joined to the geometry of the GISCO COMM_2004 regions. This was dissolved by each UA code to give the multipart regions for each UA level. Attributes were appended to each feature class by joining pre-prepared attribute tables. Creation of UA SCD2 feature classes based on communes 2004 geometry: For countries IE, MT and PT, country files listing the SCD L2 status of each EBM 2004 commune were joined to the geometry of the GISCO COMM_2004 regions. This was dissolved by each SCD L2 code to give multipart regions. Further subdivision of SCD L2 regions in the country of PT were made based on URAU_2001 geometry. Creation of UA SCD2 feature classes based on provided digital maps: For the remaining UA Cities for which SCD geometry is available, SCD L2 regions were derived from GIS files supplied by URAU delegates in various projections, coordinate systems and GIS formats. The SCD L2 regions were converted, projected and had geographic transformations applied where necessary. Some SCD L2 geometry had small manual shifts applied where the exact geographic transformation could not be defined. In the country RO, the outer SCD2 regions are not coincident with GISCO COMM_2004, and were fitted using aerial imagery. The outer SCD L2 boundaries were made coincident with UA City geometry. In the country BE, some internal boundaries were also made coincident with GISCO COMM_2004 geometry. Creation of UA SCD1: SCD attributes were appended to the SCD L2 feature class by joining pre-prepared attribute tables. SCD L1 geometry was created by dissolving SCD L2 boundaries using attributes in the supplied tables. Generalisation of polygonal feature classes to 1:3 million scale: The five polygonal feature classes were generalised for display at a scale of 1:3 Million. The geometries were combined prior to generalisation using a Union, so that boundaries shared between feature classes would also share the same simplified form. Polygons below 2.25km2 were eliminated by merging into the neighbouring polygon sharing the longest border, or deleted (for small islands). At least one feature was retained for each unique City, SCD L1, SCD L2, Kernel and LUZ. The simplification used the Bend Simplify option of the Simplify Polygon tool in ArcGIS 9.3, with a reference baseline of 1500m. Synchronisation of city points with STTL_V3: UA City points were derived by matching City regions to the GISCO Settlement Version 3 dataset (STTL_V3) based on proximity and name-matches. All except 17 UA Cities were matched, and STTL_V3 codes were retained as a UA City attribute. In several cases the STTL_V3 and UA City points were located outside the UA City regions (original or generalised). They were moved so that the point falls inside the RG, while still respecting the requirements for STTL_V3 points. Attribution of COMM_2004: The Urban Audit status of each commune was recorded by appending the City, Kernel and LUZ codes to the COMM_2004_AT attribute table.