Fig. 1. Schematic of the study area

Fig. 2. Analysis between brightness value and gray scale value at each band and SWI analysis diagram. (a) Analysis diagram between brightness value and gray scale value at green band (G); (b) analysis diagram between brightness value and gray scale value at red band (R); (c) analysis diagram between brightness value and gray scale value at blue band (B); (d) analysis diagram between brightness value and gray scale value at near-infrared band (NIR); (e) SWI analysis diagram

Fig. 3. Overlay image results after different algorithms distinguish water bodies from shadows and other ground objects. (a) Manual labeled shadow and water body; (b) LGR segmentation result; (c) SWI segmentation result

Fig. 4. Technology roadmap

Fig. 5. Water extraction results of different methods. (a) Decision tree; (b) SVM; (c) RF; (d) CNN; (e) NDWI+NIR; (f) proposed method; (g) manual visual interpretation

Table 1. Technical indexes of payload of GF-2 satellite

Table 2. Water extraction area and extraction difference

Table 3. Water extraction accuracy of various methods