Analysing the compactness of urban areas by using indicators derived from data acquired by remote sensing

Urban form is one of the main characteristics of urban areas which affects its sustainability. It has a bearing on the size of the ecological footprint of the city, degree of soil sealing, transport (length of trips and modal split), air pollution, social segregation, etc. We analyse urban sprawl by making use of land use data gathered through remote sensing. Our data source is the multi-temporal land use databank called MOLAND, which has been created and maintained by the Joint Research Centre of the European Commission. In this paper we focus on two indicators measuring the expansion of European urban areas from the mid-1950´s to the late 1990´s. The first indicator is based on the change of mean distance between the residential areas and the city centre and how it has evolved in time. The assumption is that in more sprawled cities the distance has grown more and faster than in more compact cities. There are considerably large differences among studied European urban areas. The second indicator describes the saturation of land use. Urban areas have been divided in co-centric rings the width of which is 1 km and the center point is in the city centre. The further away from the city centre the rings move the dominance of open space and forests grows. The analysis covers the period from the mid-50´s to the late 1990´s. During this period the share of built-up areas has grown in all distances but proportionally more farther away from the city centre. This indicator complements the first one. Both indicators indicate the loosening of urban structures in the studied European cities. They have proven to be solid indicators for describing some aspects linked to urban sprawl.