A worldwide model for boundaries of urban settlements

Area of Science:

• Urban Planning
• Geographic Information Science
• Computational Social Science

Background:

• Defining urban settlement boundaries is a persistent challenge in urban planning and the science of cities.
• Existing methods often rely on administrative boundaries, which can be arbitrary and limit comprehensive analysis.
• Understanding urban form is crucial for sustainable development and economic studies.

Purpose of the Study:

• To develop a universal, bottom-up model for defining urban settlements irrespective of administrative borders.
• To enable the study of urban scaling laws at global, continental, and national levels.
• To provide a more accurate and robust definition of cities for socioeconomic analysis.

Main Methods:

• A novel, bottom-up computational model was developed to delineate urban settlements.
• The model incorporates geographical biases and regional growth dynamics.
• The model's robustness was tested against established principles like Zipf's law.

Main Results:

• The proposed model successfully defines urban settlements globally, accounting for diverse growth patterns.
• The study validates Zipf's law for urban scaling across different geographical scales.
• A re-evaluation of the world's largest cities indicates discrepancies with recent United Nations reports, identifying a large agglomeration in Egypt as the most populous.

Conclusions:

• The new model offers a standardized and geographically informed approach to defining urban areas.
• This definition facilitates systematic studies of urban economies, free from administrative boundary limitations.
• The findings necessitate a revision of current understandings of global urban hierarchies and population distributions.