Comparison of Methods for Estimating Mechanical Properties of Wood by NIR Spectroscopy

Table 5

Summary of air-dry density calibrations based on radial and transverse face NIR spectra obtained using three different methods (Foss Direct, Foss Probe, and ASD Probe) for collecting spectral data. 332 samples were used to develop the calibrations.

Property/method	Number of factors	R^2	SEC	SECV	RPDc
Foss Direct
Density (kg/m^3)—radial face	8	0.81	35.6	38.5	2.1
Density (kg/m^3)—transverse face	8	0.80	36.8	38.3	2.2
Foss Probe
Density (kg/m^3)—radial face	4	0.51	57.7	59.8	1.4
Density (kg/m^3)—transverse face	10	0.68	46.8	49.5	1.7
ASD Probe
Density (kg/m^3)—radial face	8	0.73	43.2	45.8	2.0
Density (kg/m^3)—transverse face	10	0.70	45.0	48.5	1.8