Errors induced by spectral measurement positions and instrument noise in soil organic carbon prediction using vis-NIR on intact soil

•The error induced by spectral measurement positions is 18.6% of mean SOC content.•The error induced by spectral measurement positions is a third of modeling error.•The error induced by instrument noise is negligible, 1.46% of mean SOC content.•The error due to core sample positions is considerable, 12.5% of mean SOC contents.