## 3 Methodology
### Analysis of Driving Mechanism of Construction Land Change  
Drawing on existing studies, the mechanism of urban construction land expansion can be categorised as thrust, support, elasticity, and resistance [46]. thrust is the main factor driving the expansion of construction land and mainly includes demographic, economic, and transportation factors. It can be seen from the changes in construction land, economy, and population in Hong Kong over the past years (Figures 6 and 7) that construction land is positively correlated with economic and population factors and grows with the growth of economic, population, and transportation factors. The driving mechanism is that the increase in population brings about an increase in demand for basic services such as housing and education, thus promoting the construction of urban infrastructure and related works; the urban construction area shows the spatial characteristics of regional sprawl or infill. Figure 6: Line chart of Hong Kong’s GDP, 1966–2020 (Source: World Bank, IMF). As regional development reaches saturation, cities begin to seek other areas suitable for construction. With the continuous improvement of policy attention and transportation accessibility, satellite cities in the traditional sense (Tuen Mun, Yuen Long) began to form and began a new round of expansion. During this period, the multi-centre aggregation of population and economy made Hong Kong's polycentric urban structure gradually more refined. Supporting forces are the factors that provide convenient conditions for urban expansion, including the natural environment and policy factors. Hong Kong is strategically important as a shipping hub for countries around the world. Victoria Harbour gradually developed as a wide natural harbour with deep water to become one of the extremely important trading ports in Asia since 1842.Policy factors have also been an important factor in supporting the expansion of land for construction in Hong Kong. The urban development of Hong Kong during the study period was largely consistent with or slightly delayed by the policy direction, from the development and growth of new towns brought about by the Ten Year Housing Plan at the beginning of the study period, to the Port and Airport Development Strategy Study, the Metropolitan, and many other policy documents, all of which led to the gradual establishment of Hong Kong's urban development direction and urban spatial structure from the planning level. Elasticity refers to the driving forces for urban expansion in different areas of the city. Elasticity is reflected in the development of construction land in Hong Kong, and its representative phenomena are the reclamation projects in various coastal areas of Hong Kong. As a city with high-density development, reclamation projects have provided a large amount of valuable construction land. They have effectively alleviated the tense human-land conflict in Hong Kong, affecting the urbanization process and urban spatial structure of Hong Kong, and playing an important role in Hong Kong's construction land. Resistance refers to factors that hinder urban expansion, including environment protection, cultural heritage protection, etc. Hong Kong has country parks and ecological green spaces accounting for about 73.3% of the entire territory. The awareness of ecological protection is relatively higher than that of inland China. The \"Country Parks Ordinance\" enacted in 1976 clearly prohibits any form of commercial development of country parks and continues to enforced in Hong Kong. The Hong Kong British Government established the Environmental Protection Department in 1981 to address environmental problems such as waste, sewage, and noise and light pollution in Hong Kong. To preserve the style of Victoria Harbour, the government was required to stop reclamation projects. The \"Harbour Protection Association\" was established in 1995. It aimed to protect and preserve the style of Victoria Harbour and asked the government to stop reclamation projects.