A shadow- eliminated vegetation index (SEVI) for removal of self and cast shadow effects on vegetation in rugged terrains

Figures & data

Figure 1. Research data, field survey location, subarea and validation samples.

Figure 2. Schematic diagram of terrain shadows.

Figure 3. TOA reflectance of six land-cover types (left) and VI values on shady and sunny slopes (right).

Note: bands #1–2 represent red and near-infrared wavebands, respectively (left); slopes #1–2 represent vegetation on shady slopes and sunny slopes without shadow, respectively (right).

Figure 4. Curves for f (Δ) optimization.

Figure 5. Vegetation indices in the research area.

Note: a–c, j represent vegetation indices computed from the TOA reflectance data, d–f represent vegetation indices computed from the C model corrected data, g–i represent vegetation indices computed from the 6S + C corrected data, and k represents cosi.

Figure 6. Plots of vegetation indices for 532 sets of samples.

Note: a–c, j represent vegetation indices computed from the TOA reflectance data, d–f represent vegetation indices from the C model corrected data, and g–i represent vegetation indices from the 6S + C corrected data.

Table 1. Mean (M) and relative error (E) of vegetation indices in self shadows, cast shadows and sunny slopes.

VI	Data	Mself	Mcast	Msunny	Eself (%)	Ecast (%)
NDVI	TOA	0.245	0.255	0.629	61.06	59.43
	C	0.568	0.366	0.619	8.20	40.91
	6S + C	0.695	0.610	0.744	6.52	18.01
RVI	TOA	1.667	1.708	4.526	63.16	62.26
	C	3.710	2.221	4.402	15.73	49.54
	6S + C	6.136	4.482	7.337	16.37	38.91
EVI2	TOA	0.064	0.070	0.374	83.01	81.40
	C	0.336	0.137	0.352	4.58	61.04
	6S + C	1.443	1.211	1.584	8.90	23.57
SEVI	TOA	14.744	14.348	14.134	4.32	1.51

Figure 7. Scatter plots of vegetation indices and cosi with 532 sets of samples.

Table 2. Linear correlation analysis and coefficient of variation (Std/Mean) of 532 sets of samples.

VI	Data	r^2	k	d	Mean	Std	Std/Mean(%)
NDVI	TOA	0.652	0.438	0.254	0.380	0.183	48.20
	C	0.017	0.047	0.507	0.521	0.120	22.95
	6S + C	0.030	0.045	0.674	0.687	0.088	12.80
RVI	TOA	0.642	3.330	1.687	2.649	1.403	52.97
	C	0.035	0.659	3.284	3.474	1.192	34.31
	6S + C	0.033	1.097	5.722	6.039	2.042	33.82
EVI2	TOA	0.691	0.366	0.064	0.170	0.149	87.58
	C	0.001	0.008	0.274	0.276	0.118	42.81
	6S + C	0.033	0.131	1.385	1.423	0.244	17.12
SEVI	TOA	0.032	−0.960	14.770	14.490	1.825	12.59

Note: The r², k, and d are the coefficient of determination, line slope, and intercept, respectively.