## 3 Method
### Spatial Characteristics of Building Functional Types  
Buildings with the same functional type tend to have certain spatial similarities in terms of area, shape, orientation, and location. The following is an analysis of several of the spatial characteristics of the buildings in the study area. Figure 9 shows the distribution of spatial characteristics for each building function type using box plots. Buildings of different functional types have different demands on land area due to urban planning, land use types, demographic structure, etc. Among single-function buildings, the footprint of residential buildings is the smallest. The residential buildings in the city are usually designed with several floors to save land area. Office buildings are mainly used by companies and need to accommodate office workers and environmental work requirements, so have larger footprints than R. Public services buildings are of variable size. Public service buildings are typically owned by government agencies and departments at all levels. They serve as workplaces for these agencies and institutions. High floor designs can reduce the building footprint while providing more office space. Smaller agencies may have offices in buildings with smaller footprints, resulting in a wide variation in the size of public service buildings. Commercial buildings include large shopping malls, building materials markets, and small stores. Large shopping malls include and sales, logistics, and other functions, increasing the need for land area, while small stores have a relatively small land area. Mixed-function buildings generally have larger footprints than single-function buildings. For example, the footprint area of buildings with mixed residential and other functions, such as mixed residential and public service, mixed residential and commercial, and mixed residential and office is larger than that of buildings with a single residential function. The probable reason is that buildings with mixed residential types need additional space for commercial, office, or public service activities while also providing a residential function, thus increasing the demand for site space. Figure 7: Building functional identification within the Guangxi Procuratorate according to (**a**) Gaode map, (**b**) POIs, (**c**) the proposed method, and (**d**) the Tyson polygon area share method [33]. The values of the shape compactness of each type of building are concentrated in the range of 0.5 to 0.8. This indicates that the shape of most buildings is regular. The shape of single-function buildings is more regular and simpler than those of mixed-function and comprehensive-function buildings. Residential buildings are mostly high-rise buildings with simple shapes such as simple rectangles or L-shapes to maximise the available living space. Commercial buildings in large shopping centres take into account the spatial layout inside the stores and malls, and traditional office buildings and public service buildings favour regular designs such as rectangles, squares and other shapes in order to create regular office and service spaces. A small number of buildings adopt non-regular designs to show their sense of design and unique cultural connotations, such as museums, new types of business buildings, school buildings, and landmark government buildings. Buildings with mixed and comprehensive functions have more flexible and complex spatial designs to accommodate different functions, so their shapes are diverse and complex. Figure 8: Building functional identification of Nanning Daily Newspaper buildings according to (**a**) Gaode map, (**b**) POIs, (**c**) the proposed method, and (**d**) the Tyson polygon area share method [33]. Urban buildings have different needs for road access depending on their function.