Optimization of a Soil Particle Content Prediction Model Based on a Combined Spectral Index and Successive Projections Algorithm Using Vis-NIR SpectroscopyByKe Xia,Qi Cheng,Shasha Xia,Shiwen Zhang,Qiang Shen,Cheng Li,Ji ZhouDecember 1st 2020A rapid vis-NIR spectroscopy method for determining soil particle size and quality.