Context and objectives
The urban centre or ‘morphological conurbation’ is delimited by the spatial continuity of the urban housing; the adaptation of the morphological town to the boundaries of the municipality defines the ‘operational conurbation’. The latter definition is used for statistical purposes and international comparisons.
Until recently, the delimitation of the urban housing area and the evaluation of its continuity was made on the basis of interpretation of maps, orthophotoplans and aerial photographs. Since 1993, the Agency for Statistics of the European Community, EUROSTAT, has shown a special interest in the contribution of satellite imagery to urban statistics, and has financed a comparative study in the E.C. member states. The agency is presently stimulating the national statistical institutions to produce their statistics on the basis of satellite images. This study investigates whether the frequent registration capabilities and spatial resolution of the satellite images meet the requirements for updating the boundaries of the statistical sectors constituting a conurbation.
Expected scientific results
The remote sensing methodology performs well and is very fast in comparison with the exhaustive conventional method, in which surface areas are determined and measured on the basis of maps or aerial photographs. It would be interesting to combine the SPOT scene (higher spatial resolution) with a LANDSAT image (containing more thematic information) to eliminate uncertainties occurring at the classification procedure.
An estimation was made of the human resources needed to determine the conurbation boundaries in Belgium using satellite remote sensing :
- > 80.000 inhabitants : 7 mandays for image processing + 5 mandays for other processing;
- 40.000 - 80.000 inhabitants : 5 mandays for image processing + 5 mandays for other processing;
- < 40.000 inhabitants : 3 mandays for image processing + 5 mandays for other processing.
As a result of the study, the relevance of present definitions (statistical sectors, …) is being discussed.