Fig. 1. Flow chart for riparian line extraction

Fig. 2. Diagram of rough river shoreline extraction

Fig. 3. Dynamic threshold removes the high point

Fig. 4. Shoreline “burr” points

Fig. 5. Normal angle diagram

Fig. 6. Normal gradient constraint joins adjacent points

Fig. 7. Remove tidal points

Fig. 8. Remove high noise points

Fig. 9. Riverbank rough contour

Fig. 10. Real shoreline under the trees

Fig. 11. Height statistics of coarse riverbank contour

Fig. 12. Adaptive dynamic threshold correction

Fig. 13. Elevation histogram. (a) Single-peak elevation histogram; (b) bimodal elevation histogram

Fig. 14. Normal gradient constraint result. (a) Normal gradient constraint theory; (b) real shoreline under raster diagram; (c) real shoreline points in CloudCompare software

Fig. 15. Overlay of shoreline and imagery. (a) River shoreline map; (b) central island shoreline map;（c）overlapped map of extractive shoreline and actual shoreline

Fig. 16. Statistical histogram of error distribution extracted from the river edge. (a) Contour tracking method; (b) our method

Fig. 17. Extraction results comparison of our method and contour tracking method in different environments. (a) Extraction result of central island by contour tracking method; (b) extraction result of central island by our method; (c) extraction result of river bank by contour tracking method; (d) extraction result of river bank by our method

Table 1. River edge extraction error analysis table