## 2 Study Area and Data
### Data Sources and Process  
Hong Kong's urbanisation process began in 1842 with the opening of the city port, and initially urban development was concentrated on Hong Kong Island and Kowloon. As the population continued to grow and the living environment in residential areas deteriorated, the development of new towns became urgent. In 1960, the British Hong Kong Government began to plan for the development of new towns, and construction work began in 1970. In the same year, the Ten-Year Housing Programme was proposed, aiming to build low-cost housing for 1.8 million people in the new towns between 1973 and 1983, which gave a strong impetus to the rapid expansion of land for construction in Hong Kong and marked the beginning of the large-scale development of new towns. Therefore, research sets 1972 as the initial year of the study, with the aim of exploring the characteristics and driving mechanism of the evolution of construction land across Hong Kong since the launch of the Hong Kong New Town Programme. Therefore, nine periods of data were selected between 1972, 1980, 1990, 1995, 2000, 2005, 2010, 2010, 2015 and 2020, with a total time span of 48 years, which can better reflect the characteristics and changes in the distribution of construction land since the launch of the New Town Programme.  
The Geological Map of Hong Kong, Kowloon, and the New Territories (1:50,000) 1972 (hereinafter referred to as the Geological Map), the data of the National Land Use Types of the Chinese Academy of Sciences (hereinafter referred to as the CAS data), and the statistical yearbooks of Hong Kong for various historical years were used as the data for this research. The Geological Map is based on the thematic geological data of the whole territory of Hong Kong, with data on urban roads, railways, construction areas, etc., which can better reflect the development of the city at that time and be used for quantitative empirical research; thus, this historical map was selected as a history data source, and we extracted construction land data by manual visual interpretation. The CAS data were decoded and interpreted using Landsat imagery data, and the field validation showed that the  
Figure 1: Schematic diagram of the study area (original image source: Survey and Mapping Office, Lands Department of the Hong Kong Special Administrative Region).  
classification accuracy of urban construction land reached 98.26%, which meets the research needs of this paper [30; 31]. Vector data such as Hong Kong administrative divisions were obtained from the 1:1 million public version of the Basic Geographic Information Dataset released by the China National Geographic Information Centre ([[https://www.webmap.cn/main.do?method=index](https://www.webmap.cn/main.do?method=index)]([https://www.webmap.cn/main.do?method=index](https://www.webmap.cn/main.do?method=index)) (accessed on 12 February 2023) in 2021. Statistics such as GDP and population data from 1972 to 2021 were obtained from the statistical yearbooks released by the Hong Kong Government for various years (Table 1).  
We used ArcGIS to calculate the area, rate of change in construction land, intensity of construction land expansion, and the centre of gravity at each study time. The land use conversion matrix was used to analyse the data of adjacent years; Fragstats 4.2 was used to calculate the changes in the landscape pattern index of urban construction land in each time period to explore the characteristics and driving mechanism of urban expansion in Hong Kong over the past half-century.