Standard Normal Variate

Features:

Removes light scattering from the image and reduces differences in the global intensities of the signals.

Steps:

1.      Open a file. Select Data Correction tab and select Standard Normal Variate (SNV).

2.      From the pop-up dialogue window, select a Sliding Window Size. The default value is 10, which is equivalent to 10x10 pixels

The sliding window is a computational imaging technique that uses a small number of pixels in a grid of cells, of a specified size (i.e., 2 x 2) to perform calculations and reduce the calculation time. The grid of cells passes through the spatial dimension of the image. At each pass, the calculation within the window is performed and the first pixel in the window takes the values from the calculation. IDCube uses the length of one dimension as the window size.

Additional Information:

Performs a normalization of the spectra that consists in subtracting each spectrum by its own mean and dividing it by its own standard deviation. After SNV, each spectrum will have a mean of 0 and a standard deviation of 1.

When using SNV, the spectra always have positive and negative values centered on 0, which may make interpretation difficult.

SNV assumes that multiplicative effects are uniform over the whole spectral range, which is not always the case, so artifacts could be introduced by this transformation

References:

Barnes, R.J., Dhanoa, M.S., Lister, S.J. 1989. Standard normal variate transformation and detrending of near-infra-red diffuse reflectance spectra. Applied Spectroscopy 43, 772–777.