Estimating Salt Concentrations Based on Optimized Spectral Indices in Soils with Regional Heterogeneity

Table 5

Accuracy of cross-validation dataset.

Predictive models	Calibration/validation dataset	n	R^2Cal	RMSECal (g·kg^−1)	R^2Pre	RMSEPre (g·kg^−1)
Cross validation of Ebinur Lake Basin
E-model (NDSIs)	Ebinur/Ugan-Kuqa	15	0.82	3.82	0.40	10.23
E-model (RSIs)	Ebinur/Ugan-Kuqa	15	0.82	3.84	0.41	10.12
E-model(Com)	Ebinur/Ugan-Kuqa	15	0.83	3.79	0.43	9.68
E-model (NDSIs)	Ebinur/Keriya	15	0.82	3.82	0.37	11.96
E-model (RSIs)	Ebinur/Keriya	15	0.82	3.84	0.39	11.54
E-model(Com)	Ebinur/Keriya	15	0.83	3.79	0.41	10.89
Cross validation of Ugan-Kuqa Oasis
U-model (NDSIs)	Ugan-Kuqa/Ebinur	15	0.74	7.38	0.33	12.35
U-model (RSIs)	Ugan-Kuqa/Ebinur	15	0.77	10.50	0.34	12.78
U-model(Com)	Ugan-Kuqa/Ebinur	15	0.78	4.96	0.38	11.97
U-model (NDSIs)	Ugan-Kuqa/Keriya	15	0.74	7.38	0.30	11.45
U-model (RSIs)	Ugan-Kuqa/Keriya	15	0.77	10.50	0.40	11.35
U-model(Com)	Ugan-Kuqa/Keriya	15	0.78	4.96	0.42	11.14
Cross validation of Keriya Oasis
K-model (NDSIs)	Keriya/Ebinur	15	0.62	4.53	0.27	11.96
K-model (RSIs)	Keriya/Ebinur	15	0.63	4.22	0.29	11.84
K-model(Com)	Keriya/Ebinur	15	0.67	3.18	0.31	11.02
K-model (NDSIs)	Keriya/Ugan-Kuqa	15	0.62	4.53	0.28	12.57
K-model (RSIs)	Keriya/Ugan-Kuqa	15	0.63	4.22	0.29	12.58
K-model(Com)	Keriya/Ugan-Kuqa	15	0.67	3.18	0.29	12.31
Revalidation of global model
Global model	Ebinur/Ugan-Kuqa/Keriya	45	0.77	5.32	0.69	8.45