## 1 Introduction  
Cultivated land resources are very valuable, and in the current situation of scarce cultivated land resources, urban agriculture is a good solution. Urban agriculture is an agricultural production activity carried out in urban built-up areas. By tapping into the existing green production potential of cities and improving their ecological carrying capacity, it can increase the effective supply of arable land, reduce resource consumption, improve the ecological environment, bring material output, and promote interpersonal communication. It has important ecological, economic, and social significance. Since 2005, many cities and regions in Western countries have conducted land inventories using geographic information systems and aerial images to determine the land available for agricultural development in cities [1; 2; 3; 4; 5; 6] and to evaluate the production potential of urban agricultural land [5; 6; 7; 8; 9]. Currently, the development models of urban agriculture mainly include rooftop agriculture, community agriculture, vertical farms, etc. Among them, rooftop agriculture refers to the use of idle space on the roof to develop agriculture. This model not only helps to alleviate the urban heat-island effect but also can produce more green vegetables without occupying new urban construction land. The use of idle roofs for agricultural planting is also of great benefit to the landscape, bringing ecological benefits [10]. Many scholars have conducted a series of investigations and studies on the available space of building roofs in cities, focusing on inventory methods, inventory standards, and other aspects. The current practices and standards for roof space inventory are mainly as follows: [PERSON] et al. reviewed the suitability of vacant rooftop spaces in New York City, used public data to determine suitable buildings for different farming methods (including considering structural factors), and combined these data with aerial imagery to verify and estimate the available area. Boston conducted an inventory of roofs with a minimum roof area of 93 m\({}^{2}\) (1000 ft\({}^{2}\)), a maximum building height of 30.48 m (100 ft), and a surface slope of <5\({}^{\circ}\)[7]. In the inventory of rooftop agricultural production space conducted by Columbia University in New York City, the following standards were adopted: The building was located in a commercial and industrial area; the requirement for the roof to withstand a live load during construction within a certain time range was 2.4 KN/m\({}^{2}\) (50 pounds per square foot); it covered an area of over 929 m\({}^{2}\), avoiding small-scale roof planting with greater economic uncertainty; the building height was about ten stories; and the buildings could not be used for heavy industry or hazardous substance production [11]. [PERSON] et al. used LASools to generate digital terrain models and digital surface models and then used GIS to calculate roof slopes to detect roofs with slopes below 5 degrees within 69% of the total area of Rio de Janeiro and evaluate their vegetable production needs. The research results indicated that 1385 hectares of roofs within the scope of this study are suitable for agricultural cultivation, and the vegetables produced can meet 39.2% of the annual vegetable needs of residents in Rio de Janeiro [12]. [PERSON] et al. used ArcMap 10.1 and Google Earth 6.2 to analyze the industrial rooftop space in Montreal and used hydroponic methods to grow vegetables. The results showed that its yield could easily meet the city's vegetable needs [13]. [PERSON] et al. used light detection and ranging (LIDAR) and long-wave infrared (LWIR) data, Leica ALS50-II, and TASI-600 sensors to identify some building roof parameters (area, slope, material, and solar radiation) to determine the potential for building roof agriculture and applied this method to non-residential urban areas of the Rubi Industrial Estate in Barcelona, Spain.