Quantification of urban greenery using hemisphere-view panoramas with a green cover index

Figures & data

Figure 1. Calculated panoramic green cover index (PGCI) values at a human scale using hemisphere-view panoramas (HVPs). (A-C) stitching process of the hemisphere-view panorama (HVP). (D) hemisphere-view panorama equipment, which includes (1) a 360-degree panoramic camera, (2) a laptop as the controller and data receiver, (3) a mobile power source, and (4) a specific tripod. (E) workflow to the calculate PGCI value

Table 1. Areas of the four functional types in 2013, 2015 and 2018

Functional types	2013		2015		2018
	Area (km^2)	Proportion	Area (km^2)	Proportion	Area (km^2)	Proportion
R	26.02	53.10%	25.84	52.90%	25.37	51.68%
E	8.89	18.14%	9.07	18.57%	9.03	18.39%
C	7.34	14.98%	7.58	15.52%	7.62	15.52%
T	5.98	12.20%	5.98	12.24%	5.98	12.18%
Others	0.77	1.58%	0.38	0.76%	1.09	2.23%
Total	49.00	-	48.85	-	49.09	-

R: Residential area; E: Recreational area; C: Commercial area; T: Traffic area.

Table 2. Descriptive information of 12 typical quadrats in Xicheng District

Quadrat name	Abbreviation	Function type	Quadrat coordinates
Zhuangshengcheng Residential Quarter	ZSCRQ	Residential area	Lon: [116.379–116.381], Lat: [39.896–39.899]
Dongnanyuan Hutong	DNYHT	Residential area	Lon: [116.385–116.389], Lat: [39.894–39.895]
Luyuan Residential Quarter	LYRQ	Residential area	Lon: [116.339–116.345], Lat: [39.925–39.927]
Xiaohoucang Hutong	XHCHT	Residential area	Lon: [116.360–116.364], Lat: [39.937–39.940]
Yuzhongxili Residential Quarter	YZXLRQ	Residential area	Lon: [116.384–116.388], Lat: [39.970–39.973]
Xisibei Hutong	XSBHT	Residential area	Lon: [116.368–116.374], Lat: [39.928–39.931]
Taoranting Park	TRTP	Recreational area	Lon: [116.380–116.386], Lat: [39.873–39.876]
Grand View Garden	GVG	Recreational area	Lon: [116.354–116.359], Lat: [39.870–39.872]
Beihai Park	BHP	Recreational area	Lon: [116.385–116.393], Lat: [39.922–39.932]
Commercial center	CC	Commercial area	Lon: [116.353–116.365], Lat: [39.913–39.924]
Deshengmen Archery Tower	DSMAT	Traffic area	Lon: [116.379–116.381], Lat: [39.948–39.950]
Beijing Financial Street	BFS	Traffic area	Lon: [116.345–116.366], Lat: [39.907–39.924]

Lon: Longitude; Lat: Latitude

Figure 2. Distribution map of samples and quadrats in Xicheng District, Beijing

Figure 3. Land surface temperature (LST) and normalized difference vegetation index (NDVI) maps of Xicheng District. (A) LST map; (B) NDVI map

Figure 4. Green vegetation segmentation results and ground truth: I original HVP pictures; II initial segmentation results; III refined segmentation results; IV ground truth. The area in the red circle is variable Area_c in formula (1), which is called the effective area of the HVP

Figure 5. Statistics and spatial distribution of the panoramic green cover index (PGCI) in the study area. (A) histogram plot of all 97 sample points; (B) histogram plots of 4 functional areas; (C) distribution map of PGCI values at the point and quadrat levels. The HVPs of different sample points represent the human-scale cityscape, and the quadrats correspond to the block scale

Figure 6. Relationship between panoramic green cover index (PGCI) and normalized difference vegetation index (NDVI)

Figure 7. Relationship between panoramic green cover index (PGCI) and land surface temperature (LST)