Table 3.

Grain yield correlations in LOW with all proximal remote sensing variables from the RGB images taken from the UAV aerial platform, RGB images from the ground, and leaf chlorophyll content (SPAD) and normalized difference vegetation index (NDVI) field sensors. These indices are defined in Section 1 and Section 2. Levels of significance: *, P < 0.05; ***, P < 0.001. GGA; GA; NDLab, normalized difference between a* and b*; NDLuv, the normalized difference between u* and v*; CSI, crop senescence index; TGI, triangular greenness index; and NGRDI, normalized green–red difference index.

GY
UAV RGB VIs	r	P	Ground RGB VIs	r	P	Additional Field Sensors	r	P
GGA	0.445	***	GGA	0.483	***	SPADV (18/02/16)	0.542	***
GY	0.407	***	GA	0.466	***	SPADR (01/03/16)	0.506	***
Hue	0.381	***	Hue	0.485	***	NDVI	0.375	***
Intensity	−0.305	***	Intensity	0.095
Saturation	−0.427	***	Saturation	−0.227	*
Lightness	−0.291	***	Lightness	0.144	*
a*	−0.36	***	a*	−0.383	***
b*	−0.397	***	b*	−0.089
u*	−0.383	***	u*	−0.449	***
v*	−0.297	***	v*	0.014
NDLab	0.359	***	NDLab	0.468	***
NDLuv	−0.378	***	NDLuv	0.442	***
CSI	−0.428	***	CSI	−0.321	***
TGI	0.229	*	TGI	−0.043
NGRDI	0.406	***	NGRDI	−0.027