The results showed that the two vegetation indexes (NDVI and RENDVI NDVI and MTCI OSAVI and RENDVIOSAVI and MTCI and MTVI2 and MTCI) could be used to further increase the GPC estimation accuracy (Table 3).
1b)and three vegetation indexes (SIPI OSAVI and MTVI2R2=0.
Results of this study showed that the GPC could be effectively estimated using single vegetation indexes (MTVI2 MCARI MCARI/MTVI2 TCARI TCARI/OSAVI SIPI PPR DCNI CIred edge MTCI and RENDVI) (Table 2) two vegetation indexes (NDVI and RENDVI NDVI and MTCI OSAVI and RENDVIOSAVI and MTCI and MTVI2 and MTCI) (Table 3) three vegetation indexes (NDVI SIPI and MTVI; NDVI RENDVI and CIred edge;
NDVI MTCI and MCARI; SIPI RENDVI and MTVI2; SIPI OSAVI and MTVI2) (Table 4) and partial least squares (PLS) (Table 5).
PLS(a)###RENDVI MTVI2 MTCI OSAVI SIPI CIred edge MCARI and NDVI###0.
PLS(b)###NDVI SIPI PPR RENDVI RENDVI MTCI DCNI TCARI OSAVI TCARI/OSAVI###0.
The results indicated NDVI, OSAVI
, SAVI, and TSAVI were better spectral parameters to monitor in irrigated land, but DVI, RDVI, TSAVI, and SAVI were better spectral parameters to monitor in dryland (Table 5).
When estimating vegetation fractional coverage with OSAVI
and MSAVI2, the optimal combination of bands was 687 or 690 nm (red), depending on the model, and 952 nm (NIR), which is slightly different from the optimal combination for the other two vegetation indices and clearly different from the frequently used combination of 670 nm (red) and 800 nm (NIR).