## 3 Data Sources and Research Methods  
### Research Area and Data Sources  
Based on the \"Xi'an City National Land Space Master Plan (2020-2035)\" (hereinafter referred to as \"The Plan\"), this study selected the central urban area of Xi'an as its focal research zone [63]. The central urban area is pivotal, serving as the heart and central hub of Xi'an. It functions as the core area for the city's spatial expansion, population aggregation, commercial activities, and tourism development [64]. \"The Plan\" specifies its spatial boundaries, extending from the Wei River to the north to the S107 provincial road to the south and including Hongqing Street and Dawang Town to the east and west, respectively. This delineated area encompasses all six urban districts--BEILI, XINCHENG, LIANHU, YANTA, WEIYANG, and BAQIAO--along with parts of Chang'an District and XiXIAN New Area, covering a total area of 1641.11 square kilometers. By the end of 2023, it is projected to host a permanent population of approximately 11 million and generate a GDP of about 1 trillion yuan (Figure 3). \"The Plan\" categorizes the central urban area into four distinct tiers: the first tier, which lies within the Ming Dynasty city walls and serves as the primary area for Xi'an's historical, cultural, and tourism activities; the second tier and the first tier, which act as the traditional population center and a focal point for science and education; the third tier to the second tier, designated as the zone for commercial trade and industrial activities; and the fourth tier, identified as the future urban expansion carrying area. This tiered structure not only reflects the historical and cultural stratification of the city but also outlines the urban development strategies aimed at enhancing socio-economic growth, improving infrastructure, and fostering sustainable urban expansion as guided by the latest planning initiatives. The decision to select Xi'an's central urban area as the primary research area was based on several compelling factors that underscore its relevance for a comprehensive spatial and socio-economic study. This area is characterized by its typical spatial distribution patterns, a well-developed socio-economic framework, a robust and extensive transportation network, and prominent commercial service offerings. Additionally, it exhibits a high level of urbanization, a rapid pace of lifestyle, and elevated demands for quality of life, making it an exemplary urban center for in-depth analysis. Moreover, the central urban area of Xi'an holds considerable promise for predictable development trajectories, especially given the momentum of the \"Belt and Road\" initiative, which further enhances its strategic importance. The availability of diverse datasets and the feasibility of material acquisition also played a crucial role in its selection as the study location. Base map data were meticulously sourced from the National Geographic Information Resources Catalogue Service System (www.webmap.cn, accessed 11 February 2024), ensuring a reliable geographic framework for analysis. The acquisition of Point of Interest (POI) data was executed through advanced Python scripts utilizing requests and json libraries, which enabled the dynamic collection of data from Amap's location service APIs for the periods of December 2012 and December 2023. These data were meticulously converted to the WGS-1984 coordinate system  
Figure 3: Study Area of Xi’an City Center. to ensure accuracy and compatibility with global data standards. Furthermore, detailed information on the distribution of roads, rivers, and subway lines was extracted from the OSM open-source website (www.openstreetmap.com, accessed 11 February 2024), providing a comprehensive understanding of the infrastructural elements that shape the urban landscape. Additional socio-economic development data were rigorously compiled from the \"Xi'an Statistical Yearbook\", offering a robust basis for analyzing trends and projections within the central urban area.