Analyzing building stock using topographic maps and GIS
Building stock is an extremely cost-intensive and long-lived component of the settlement structure. Considering its importance, the information available on building stock and its development is often inadequate. Data such as the age and structure of buildings, the number of dwelling units and floors are not comprehensively available nor sufficiently processed. In order to fill this gap, this paper presents a method for the calculation of settlement structure parameters by means of a spatial disaggregation through a combination of building data obtained from topographic maps 1:25 000, block boundaries taken from authoritative digital maps, and statistical data at municipality level. The inexpensive analogue maps are available nationwide and also for earlier time slices due to defined update intervals. The maps are scanned at high resolution and geo-referenced. The building stock, which is shown interspersed with traffic, vegetation and lettering, is filtered out by means of digital image processing. Buildings are then surveyed, relations to neighbouring buildings interpreted, and the general physical structure and block boundaries classified. Density can then be calculated either for the block boundaries or a reference geometry of one's choice (e.g. regular raster cells). By combining building type with typical reference density values for floor number and building area-related dwelling and resident densities, further settlement structure parameters can be calculated. Comparing the building stock on maps representing different time slices enables the development of the built environment to be analysed. The method has been implemented as a toolbox in Geographical Information System (GIS) software ESRI ArcGIS and is intended for use as a nationwide monitoring system of settlement and open space development.