Fig. 3.

Comparison of multivariate methods on early and latewood of Spruce without previous background subtraction based on 4 endmembers. Endmember spectral signatures corresponding to the intensity maps shown in Fig. 2: VCA (in red), NMF (in black), MCR-ALS without PCA (in blue) and MCR-ALS with PCA (in green). The spectra are normalized against the main aromatic band at 1600 cm⁻¹ except for EM1 and EM4