Table 5.

Statistical parameters of validation for conventional indices and artificial neural network (ANN) models.

Multispectral Index/ANNModel	MAE (MPa)	RMSE (MPa)	RE (%)	d
Multispectral indices
NDVI *	0.25	0.32	−24.22	0.54
GNDVI *	0.27	0.34	−25.58	0.51
MSR *	0.26	0.33	−24.57	0.53
ANN models
ANN-1 **	0.1	0.12	−9.21	0.82
ANN-2 **	0.1	0.12	−9.11	0.82
ANN-3 **	0.11	0.13	−9.68	0.8
ANN-4 **	0.12	0.15	−11.55	0.78
ANN-5 **	0.13	0.15	−11.61	0.77
ANN-6 **	0.15	0.2	−15.2	0.73
ANN-7 **	0.19	0.22	−16.5	0.66

MAE = mean absolute error, RMSE = root mean square error, RE = relative error, d = index of agreement. * p < 0.05, ** p < 0.01.