Segtnan, V.H., Mevik, B.-H., Isaksson, T., Næs, T. (2005); Low-cost Approaches to Robust Temperature Compensation in Near Infrared Calibration and Prediction Situations; Applied Spectroscopy (in press).
Abstract:
The traditional way of handling temperature shifts and other
perturbations in calibration situations is to incorporate the
non-relevant spectral variation in the calibration set by for instance
measuring the samples at various conditions. The present paper
proposes two low-cost approaches based on simulation and prior
knowledge about the perturbations, and these are compared to
traditional methods. The first approach is based on augmentation of
the calibration matrix through adding simulated noise on the
spectra. The second approach is a correction method that removes the
non-relevant variation from new spectra. Neither method demands the
exact knowledge of the perturbation levels. Using the augmentation
method it was found that a few, in this case four, selected samples
run under different conditions gave approximately the same robustness
as running all the calibration samples under different conditions. For
the carbohydrate data set, all robustification methods investigated
worked well, including the use of pure water spectra for temperature
compensation. For the more complex meat data set, only the
augmentation method gave comparable results to the full global model.