3. Algorithm development and testing
Reliable and repeatable classification performance for real-time plant discrimination, using discrete spectral reflectance measurements, requires the identification of a set of spectral reflectance features for the target crops/weeds.
3.1. Spectral reflectance and defined discrimination parameters
The line scan sensor captures the diffuse, reflected light intensity from illuminated targets at the wavelengths (k) 635 nm, 685 nm and 735 nm. The inferred target reflectance (Holland et al., 2012) for the individual beam-spots i, denoted as Rk[i], is calculated using the expression:
Rk½i ¼ Vk½iNk½i for i ¼ 1::512 where Vk[i] is the measured sensor response, in digital numbers of the ith beam and Nk[i], a normalisation factor for each beam, calculated as:
Pref
Nk½i ¼
Pk½i
The value Pref is a reference beam optical power (BOP) and Pk[i], the optical power of the ith beam at wavelength k