## 3 Results
### Space Service Capability Assessment  
In terms of the spatial service pattern, according to the \"Urban Environmental Sanitation Facilities Planning Code\", considering the walking speed of pedestrians and the actual demand for public toilets, a buffer zone is set according to the 500 m service range of public toilets [47; 48], and the service range of public toilets is shown in Figure 9. In 2008, the service range of public toilets was 91.61 km\({}^{2}\), mainly concentrated inside the second ring road, and some regions inside the ring road were still not covered. The service area of public toilets in 2018 is 252.88 km\({}^{2}\), mainly concentrated inside the second ring road, basically covering all regions. Because the population density inside the second ring road is high, there is a high demand for shopping places and transportation facilities with many public toilets, so a large number of shopping centers and large buildings have been built, meaning to increase the number of dependent public toilets. Simultaneously, with the further promotion and development of the toilet revolution, many new independent public toilets have been added in regions such as scenic spots, which improve the coverage of public toilets to a certain extent, enhance the service capacity of public toilets, and alleviate the tight demand for public toilets within urban regions. In terms of the overall directional distribution, one standard deviation is used to construct an ellipse, which covers 68% of the POI data of public toilets. The area covered by the standard deviation ellipse in 2008 was 79.36 km\({}^{2}\) with a perimeter of 34.93 km. The area covered by the standard deviation ellipse in 2018 was 109.64 km\({}^{2}\) with a perimeter of 43.21 km. The overall distribution range of public toilets shows an expansion trend from northeast to southwest. The oblateness of the ellipse increases and the directionality of the distribution of public toilets becomes more obvious. The main service object of public toilets is the floating population and traveling residents [49; 50]. Considering the main gathering places and the main travel destination of the floating population, seven main factors affecting the floating population from the POI data in 2018 were input into the geodetector model. The seven main factors include scenic spots, transportation facilities, shopping services, catering services, business residences, science and education, and accommodation services. The specific types contained in the POI data are shown in Table 2.  
Figure 9: Distribution of standard deviation ellipse and 500 m coverage of public toilets: (**a**) distribution of SDE and 500 m coverage in 2008; (**b**) distribution of SDE and 500 m coverage in 2018. The spatially driven factor variables of the geo-detector need to be discretized to ensure the accuracy of interpretation. According to the natural break method of five to ten classes, scenic pots were classified into eight classes, transport facilities into ten classes, shopping service into five classes, catering service into five classes, business residence into seven classes, science and education is divided into eight classes, and accommodation services are divided into eight classes. Through the calculation of the geo-detector model, the driving force values of the seven influence factors on the spatial distribution of public toilets, dependent public toilets, and independent public toilets are shown in the table. Among the seven influence factors, scenic spots had the strongest driving effect, and accommodation services had the weakest effect. They passed the significance test. For the overall distribution of public toilets, scenic spots, transport facilities, shopping service, and accommodation service passed the 5% significance level test, and catering service passed the 1% significance level test.