“…Other method utilises the direct standardisation (DS) [ 38 , 41 , 42 , 43 ] methodology which removes environmental factors (e.g., temperature, texture of soil surface, etc) from the spectroscopic database to make the library data more suitable for field data usage. Similar techniques such as the piecewise direct standardisation (PDS) [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], the slope/bias (S/B) correction [ 50 ] and the orthogonal signal correction (OSC) [ 50 ] have also been applied and better prediction of SOM have been achieved when it is compared directly with that using the raw spectral data for the analysis. Other stream of model transfer approach that utilises non-standard samples, such as the standardisation of spectra through finite impulse response (FIR) method [ 51 ], has been an alternative way to achieve similar result as that of the PDS technique.…”