High-Resolution Mapping and Analysis of Urban Green and Gray Infrastructure: A Case Study of Bavaria Using 20cm Orthophotos

Kurzfassung

Urban green and gray infrastructure play a critical role in enhancing climate resilience, mitigating urban heat islands, and improving the quality of life in cities. However, the lack of high-resolution, state-wide data on the spatial distribution of green and gray infrastructure has hindered detailed analysis and effective urban planning. This study addresses this gap by leveraging 20 cm orthophotos and geodata from official surveying to provide a comprehensive mapping and analysis of green and gray infrastructure across Bavaria, Germany. The research aims to (1) map green and gray infrastructure across all urban settlements in Bavaria, (2) compute key metrics for quantifying and characterizing green and gray infrastructure, and (3) generate zonal statistics for different administrative units to support sustainable land-use planning. Using a combination of high-resolution orthophotos, the Basic Digital Landscape Model (Basis-DLM®), building footprint data and numerical height models (DOM1), urban areas were classified into four land cover classes: gray impervious surfaces, green open spaces, trees/hedges, and buildings. The study also calculated green area per capita and green and gray proportion for categorized municipalities/cities. The results reveal that gray infrastructure (52.4%) slightly outweighs green infrastructure (47.6%) in Bavarian settlements, with significant disparities in green space accessibility between urban and rural areas. The findings validate the hypotheses that (1) high-resolution orthophotos significantly improve the identification of green and gray infrastructure patterns compared to coarser-resolution datasets, and (2) cities with a higher total proportion of unsealed land do not necessarily rank highest in green area per capita. The study demonstrates the potential of using official surveying data for detailed urban mapping and provides actionable insights for improving green space accessibility and mitigating the effects of urbanization.