Dear Mohammad, the continuum removal (or convex hull) technique is used to normalize reflectance spectra so you can compare individual absorption features or entire spectra from a common baseline. The “continuum” is a convex hull and the spectra are normalized by setting
the value of the hull to 100% . Removal of the continuum results in a normalization of the spectra and allows for comparison of absorption depths from a common baseline. Please see the figures in the topic “Method and software” for illustration and refer to the references given in the resources section. Hope this helps.