Objective  The West Lake Temporary Imperial Palace holds a position of great significance as a representative historical site encompassed within the UNESCO-designated cultural heritage complex referred to as the “West Lake Cultural Landscape”. Located at the southern foot of Gushan Mountain, the palace lies at the top of Gushan Mountain to the north and beyond the West Lake to the south. By merging the distinctive features of the royal palace gardens in Qing Dynasty and the Jiangnan mountain gardens, the West Lake Temporary Imperial Palace Garden exhibits a unique garden style and holds significant artistic and research values. Notwithstanding that the West Lake Temporary Imperial Palace has drawn increasing attention from scholars in recent years, relevant researches primarily focus on the analysis of garden space and the evolution of overall pattern, while the spatial characteristics thereof are mostly described by traditional methods that lack accuracy and quantitative conclusions. With the advent of digital measurement technology, it is now possible to achieve high-precision, non-contact and digital collection of spatial information, thereby effectively enhancing the accuracy of surveying and mapping. Furthermore, the aforesaid technology can also enable more quantitative research and analysis of the garden, and provide new ideas and methods for the research of traditional gardens.

Method  This research, by virtue of digital surveying and mapping, analyzes the spatial characteristics of the West Lake Temporary Imperial Palace Garden, which boasts a well-preserved historical layout. In addition, the research conducts a field research in conjunction with a literature review to obtain the original point cloud data about the site of the West Lake Temporary Imperial Palace Garden, with 3D laser scanning being adopted as the primary measurement method. The original point cloud data obtained is processed using SCENE 2019.0 software, based on which a 3D point cloud model is built for the garden to supplement missing historical building models.

Results  The spatial characteristics of the West Lake Temporary Imperial Palace Garden are summarized through quantitative analysis of the overall pattern, spatial perception, and line of sight thereof. 1) The planning of the West Lake Temporary Imperial Palace Garden involves opening up a four-layer terrace in alignment with the mountainous terrain. Limited by the terrain, the four layers are mostly narrow and elongated spaces extending in an east-west direction. Courtyards are arranged separated from each other with courtyard walls, forming a unique layout of scenery. To increase the depth of courtyard, the Zhuyue Spring, Jiuxiang Pavilion, and Yulan Hall courtyards are arranged in a horizontal parallel form. The width of courtyard is larger than the depth due to terrain limitations, with a width-to-depth ratio of 3∶5. Courtyard spaces serve different functions, such as drama viewing and sightseeing activities. In contrast to the courtyard layouts on the mountainside and at the foothills, the scenic spots located at the ridge are arranged linearly within a distance range of 23-35 m. Horizontal strip spaces serve as a visual guide for visitors. 2) The spatial experience of touring the West Lake Temporary Imperial Palace Garden is characterized by four changes from a closed to an open environment, with the degree of change deepening over time. Specifically, when touring the West Lake Temporary Imperial Palace Garden, you may experience a continuous jump between open and closed spaces, which creates a sense of psychological anticipation, enhances associations, and culminates in an extremely open and bright space at the ridge line. The multiple turns of touring paths and the variations in elevation differences between terrace layers provide various scenic spots with overlapping views, forming a rich set of views. Notably, the courtyard area of Zhuyue Spring features a clear line of sight relationship between the Guangbi Pavilion on the first layer and the Kanbi Pavilion on the second layer. Through the use of borrowing scenery, the ridge line showcases the external scenery of West Lake, expanding the perception space of the West Lake Temporary Imperial Palace Garden.

Conclusion  This research puts forward recommendations for the current garden restoration through the lens of restoring the historical spatial ambiance. 1) It is suggested that the existing plants on the third and fourth floor should be properly pruned, removed or replaced; 2) it is recommended to set up identification of historical architecture not yet been excavated or transformed, and set up relevant interpretation facilities. The research further summarizes the technical aspects and benefits of analyzing traditional garden spaces by digital surveying and mapping technologies, with a view to offering valuable insights into the research and preservation of comparable traditional gardens.