Normalizing reflectance from different spectrometers and protocols with an internal soil standard

The internal soil standard (ISS) concept in which a soil standard sample, exhibiting stable spectral performance, is used to normalize and align all other soil spectral measurements – was further examined herein. Different spectrometers (Spectral Evolution and ASD Spectral Pro) were used to measure a set of soil samples with the soil standards sample as a reference. Two sand dune samples served as the ISS to align measurements made under different conditions and the results were compared. It was shown that the ISS method was able to correct the spectral information from one spectrometer to another; however, the differences in the results obtained when using the two different soil standards are discussed. The main conclusion of this paper is that the soil spectral user community should adopt the ISS method for the benefit of all, and the sooner the better. This will allow much more effective exploitation of all data sets acquired on a daily basis by the growing soil spectral community that still lacks standardization procedures.