Table 3.

The collection between measured and estimated SM in four groups with respect to the NDVI values.

Study Area	NDVI	NDVI ≤ 0.27	0.27 < NDVI ≤ 0.32	0.32 < NDVI ≤ 0.36	0.36 < NDVI
Henan	r	0.7336	0.7474	0.6605	0.6092
Study area	NDVI	NDVI ≤ 0.24	0.24 < NDVI ≤ 0.28	0.28 < NDVI ≤ 0.34	0.34 < NDVI
Naqu	r	0.8021	0.7884	0.6835	0.6281