Understanding Regional Spatiotemporal Changes in 3D Building Density and Built-Up Expansion

To align with the principles of sustainable development, it is essential to understand the dynamics of urban transformation, particularly the mechanisms of building renewal, renovation and new construction. Monitoring the evolution of building volumes and the expansion of constructed area enables a better understanding of urban densification dynamics and supports evidence-based spatial planning. To address this question, this study integrates cadastral and LiDAR data to quantify residential building volume changes in Wallonia (Belgium) between 2010 and 2020. The primary reference data is derived from official regional cadastral records, which primarily describe parcel-level attributes rather than building characteristics. For residential buildings, critical data gaps exist, such as missing building types or floor counts. To address these gaps, we integrate LiDAR-derived height data (Digital Surface Models and Digital Terrain Models) with calibrated cadastral records for 2010 and 2020, ensuring accurate classification of building typology and volume estimation. The volume is estimated for each building by multiplying the footprint area by the building height. The 3D building density is calculated by dividing the sum of the building volumes within the zone of interest by the area of the zone of interest. In addition, the 3D density index is mapped at multiple scales to compare the differences in spatial development of the Belgian territories. Lastly, economic factors such as land values and house prices, as provided by the Federal Public Service Finance (Belgium), are included to study their influence on the expansion and renewal of the urban building stock.