A novel ecological evaluation index based on geospatial principles and remote sensing techniques

Figures & data

Figure 1. The natural color image showing the study areas of Fuzhou’s main urban area (a) and the zijin mining area (b).

Table 1. The acquisition dates of each image and the average meteorological data for the five days preceding each acquisition date.

Area	Image acquisition date	Average meteorological data for the five days prior to the date of image acquisition
		Temperature (℃)	Humidity (%)	Participation (mm)
Fuzhou	10-22-2001	21.52	68.31	0
	10-23-2013	21.8	64.98	0
	10 October 2020	22.3	63.62	0
Zijin	10-20-1992	18.8	N/A	0
	10 August 2014	24.3	62.88	0
	10-28-2018	21.2	74.48	0
	10-24-2020	23.1	65.05	0

Figure 2. Feature spaces showing the principles for the construction of GEI.

Figure 3. Fitted soil lines of Fuzhou city in 2001, 2013, and 2020.

Figure 4. PVI images of Fuzhou City in 2001, 2013, and 2020.

Figure 5. MPDI images of Fuzhou city in 2001, 2013, and 2020.

Figure 6. NDSI images of Fuzhou city in 2001, 2013, and 2020.

Figure 7. LST images of Fuzhou city in 2001, 2013, and 2020.

Figure 8. GEI analysis results of Fuzhou City in 2001, 2013, and 2020.

Table 2. Typical field inspection sites in Fuzhou City with their corresponding GEI values.

	Image	GEI	Land Cover Estimation	Description
1		0.5603	Vegetation cover is 67%, bare soil area is 22%, and buildings account for 11%	National Forest Park, with high vegetation coverage in most areas, but mixed by cultivated lands and buildings.
2		0.5559	Trees, grasslands, shrubs, etc. account for 58%, bare soil area accounts for 19%, and construction land and buildings account for 23%	Guling area, high elevation, characterized by vegetation coverage and temples, with low land surface temperatures.
3		0.4802	Vegetation cover is 45%, 10% is covered by bare soil, and 45% is covered by construction land and buildings	Wushan area within the old downtown area, a number of trees are planted around various old buildings. The tree canopy is large, and the vegetation coverage is medium to high.
4		0.3639	Grassland and vegetation account for 20%, bare soil area accounts for 3%, and construction land and buildings account for 77%	Sanfang Qixiang, an old town area situated in the city center, primarily consisting of streets and ancient buildings with limited vegetation coverage.
5		0.3889	The area of sandy land is 55%, the area of beaches and wetlands is 30%, and the area of water is 15%	Langqi Island beach located by the sea, with a moist surface predominantly covering with sands.

Figure 9. The 2020 image of Fuzhou (left) and its corresponding GEI (center) and RSEI (right) images.

Figure 10. Fitted soil lines of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 11. PVI images of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 12. MPDI images of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 13. NDSI images of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 14. LST images of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 15. GEI images of the zijin mining area in 1992, 2014, 2018, and 2020.

Figure 16. Change of GEI values over the study years in the zijin mining area.

Table 3. Typical field inspection sites in the zijin mining area and their corresponding GEI values.

	Image	GEI	Land Cover Estimation	Description
1		0.5255	50% is covered by vegetation and 15% by water. Bare soil accounts for 20%, and buildings and construction land account for 15%	The mountains adjacent to a tailings pond, predominantly covered with vegetation.
2		0.4289	Vegetation covers 37% of the site, and buildings and construction lands account for 63%	A building and a square nestled against the mountains, features lush vegetation coverage mixed with artificial surfaces.
3		0.283	Sparse grassland and shrubs accounted for 5%, and bare soil accounted for 95%	An expansive mining area with a vast bare surface and limited vegetation.
4		0.276	Dry and yellow grassland accounts for 15%, and bare soil accounts for 85%	A slope side with a sparse vegetation cover and a significant amount of soil exposed.

Figure 17. Comparison of the standard false-color synthesized gaofen-1 16m-resolution images with the GEI 30m-resolution image. (a) Entire area validation, left: gaofen-1 image, right: GEI image; (b) local area validation (area 1); and (c) local area validation (area 2).

Figure 18. Original image (left), GEI image (centre), and RSEI image (right) of the zijin mining area in 1992.