Validation of sentinel-2 leaf area index (LAI) product derived from SNAP toolbox and its comparison with global LAI products in an African semi-arid agricultural landscape

Figures & data

Table 1. Descriptive statistics of measured LAI (m² m^–2) used for validating SNAP-derived LAI.

Crop type	Number of plots	Min	Mean	Max	Standard deviation
Overall	65	1.49	3.86	5.83	1.23
Maize	31	1.54	3.62	5.42	0.98
Sunflower	34	1.49	4.07	5.83	1.40

Figure 1. Scatterplots and associated statistical metrics for observed (in-situ) Leaf Area Index (LAI) against predicted LAI from Sentinel-2 at 10 m (a and b) and 20 m (c and d) using Biophysical processor within SNAP Toolbox. Figure 1(a,c) show observed LAI against predicted LAI from TOA data, while Figure 1(b,d) show observed LAI against predicted LAI from BOA data.

Table 2. Separability metrics for SNAP LAI distributions with MODIS LAI (MCD15A3 H) and Proba-V LAI products at 500 m and 300 m spatial resolutions, respectively. JM-distance values closer to 2 indicate complete separability between LAI values from SNAP and MODIS/Proba-V LAI, while values < 1 indicate poor separability. M-Statistic < 1 indicates poor separability, while M > 1 indicates good separability.

	SNAP LAI from TOA		SNAP LAI from BOA
	MODIS	Proba-V	MODIS	Proba-V
JM-distance	0.09	0.19	0.13	0.25
M-Statistic	0.29	0.36	0.35	0.41

Figure 2. Scatterplots of MODIS LAI (MCD15A3 H) against SNAP-derived LAI at 500 m (a and b), and Proba-V LAI against SNAP-derived LAI at 300 m (c and d). Figure 2(a,c), are results for MODIS/Proba-V LAI against SNAP-derived LAI from TOA data, while Figure 2(b,d), are results for comparison with SNAP-derived LAI from BOA data.