Assessing the suitability of settlement delineations for monitoring infilling: A web- and GIS-based expert evaluation approach

21 st century urbanisation features not only the growth of city populations but also the emergence of densification (infilling) as significant trends in urban development. While urban sprawl has long been acknowledged for its adverse effects, understanding densification remains challenging due to inadequate empirical and statistical frameworks. This study investigates the suitability of different geospatial datasets and methods for delineating settlement areas and assessing infill housing, an aspect crucial for urban planning and development. Quantitative and qualitative analyses reveal notable variations in the classification of settlement areas and infilling across datasets. Quantitatively, the study shows distinct differences in the delineation of settlement areas, with the share of infilling varying significantly. Qualitatively, expert assessments highlight the strengths and weaknesses of datasets regarding their accuracy and consistency, revealing that the method to delineate settlement areas significantly impacts the balance between infilling and greenfield development. The study underscores the need for a nuanced approach to conceptualising densification measurement, particularly in defining urban boundaries.