Table 2. The fitting equations and their accuracies estimated by common spectral indices.

Indices	r	Fitting equation	R2cal	RMSEC	R2val	RMSEP	RPD
NDVI	0.466	y = −30.66x+41.791	0.398	4.203	0.664	3.154	0.871
NDVI705	0.465	y = −33.709x+36.614	0.398	4.203	0.663	3.170	0.901
RVI	0.461	y = −2.984x+36.058	0.399	4.200	0.662	3.247	0.987
NDCI	0.466	y = −44.116x+49.425	0.401	4.195	0.659	3.181	0.847
GNDVI	0.452	y = −37.084x+42.524	0.382	4.258	0.654	3.196	0.897
OSAVI	0.437	y = −31.458x+40.177	0.368	4.308	0.652	3.280	0.986
NDRE	0.457	y = −38.105x+36.717	0.393	4.222	0.649	3.233	0.918
mNDVI705	0.477	y = −27.917x+41.049	0.418	4.132	0.643	3.188	0.830
VOG1	0.431	y = −19.775x+53.052	0.365	4.318	0.633	3.326	0.988
VOG3	0.422	y = 79.265x+32.097	0.351	4.366	0.625	3.279	0.933
VOG2	0.424	y = 69.876x+31.809	0.353	4.358	0.622	3.288	0.938
CARI	0.378	y = −21.331x+39.558	0.308	4.506	0.605	3.523	1.180
MTVI1	0.354	y = −24.908x+35.067	0.292	4.560	0.604	3.709	1.469
TVI	0.325	y = −0.799x+35.303	0.263	4.652	0.584	3.826	1.649
DVI	0.348	y = −40.556x+35.793	0.289	4.567	0.583	3.769	1.515
RDVI	0.355	y = −41.61x+46.336	0.293	4.556	0.580	3.705	1.388
SPVI	0.348	y = −27.198x+35.464	0.289	4.568	0.575	3.761	1.466
WI/NDVI	0.414	y = 10.046x+7.791	0.371	4.297	0.540	3.623	0.870
EVI	0.062	y = −18.21x+31.547	0.372	4.292	0.524	3.759	1.206
NVI	0.406	y = −18.21x+31.547	0.372	4.292	0.524	3.759	1.206
MSAVI	0.273	y = −16.695x+21.407	0.227	4.764	0.509	4.156	2.170
WI	0.238	y = −45.663x+65.717	0.177	4.915	0.474	4.131	2.022
REP	0.343	y = 0.162x+−98.259	0.305	4.516	0.460	3.936	0.987
PRI	0.364	y = −198.981x+16.402	0.332	4.427	0.449	3.898	1.157
MTVI2	0.018	y = −0.041x+24.633	0.021	5.360	0.432	5.222	0.889
TCAR2	0.253	y = −47.674x+35.662	0.201	4.842	0.430	4.141	1.782
TCARI/OSAVI	0.350	y = 113.241x+5.231	0.336	4.414	0.419	4.204	0.910
MCARI/OSAVI	0.350	y = 339.723x+5.231	0.336	4.414	0.419	4.204	0.910
TCAR1	0.068	y = −88.168x+31.782	0.052	5.275	0.153	4.969	1.366
MCARI	0.068	y = −264.505x+31.782	0.052	5.275	0.153	4.969	1.366