First Derivative

Features:

• Generates the first derivative of the spectra.

• The first derivative of the spectrum from the region of interest is performed in two steps. First, the function averages the spectra from the region of interest. Second, the algorithm performs derivation of the spectrum, converting the mean spectrum into its corresponding first derivative spectrum.

Steps:

1.       Load the file. Select Spectra Mathematics and select First Derivative.

2.       Press Select 1st spectrum. Draw a region of interest. A spectrum corresponding to the average spectrum of the selected region will appear in the SPECTRAL ANALYSIS panel.

3.       Press Generate and observe a new spectrum.

Note: You can save the spectra using the brushing mode available from the Strip Toolbar. 

Alternative:

You can also execute the first derivative of the entire dataset selecting the First Derivative from Image Algebra available from the DATACUBE MATHEMATICS panel.

Additional Information:

A first-order derivative is the rate of change of intensity with respect to the band/channel number. A first-order derivative starts and finishes at zero. It also passes through zero at the same wavelength as the max of the band. Either side of this point is positive and negative bands with maximum and minimum at the same wavelengths as the inflection points in the band. This bipolar function is characteristic of all odd-order derivatives.