A spectral imaging device for determining a growth stage of a biomass resource. The device comprising one or two (stereoscopic) cameras and an active illumination means emitting a spectral wavelength. The cameras adapted to capture at least two images comprising data captured in the spectral wavelength emittable by the active illumination means. A processor adapted to analyse at least one image； and wherein images captured by stereoscopic camera generates a 2D and/or a 3D image.
