The 4 Channel Combination controls are used to create a basic linear combination of spectral bands. There are two sets of controls. The top of the controls shows the spectra, while the bottom half gives the linear combination option:

Image 1: Four Channel Combination Controls Window

• 4 Channel Combination Equation - Changes the wavenumber displayed in the image by entering in a new value and hitting Enter or use the pull down menus to select a band.
• Compute New Field - Computes the expression. The resulting image will show up in the Field Selector under the "Multispectral" field in the Fields tab.

Use the Shift+left click+drag combination to create a box of a region to zoom in on. To return to the full spectra, use Ctrl+left click. The Middle click+drag probing feature will list the wavelength/wavenumber as well as the reflectance or Brightness Temperature at a point along the spectra. Use the Left click+drag option to move the spectra selector bar(s) to a different value. The new value for where the spectra bar was moved to will be updated in the field at the bottom of the window.

The 4 Channel Combination tool allows for specifying arithmetic expressions for four spectral bands. Use the pull down menus between variables to select the appropriate arithmetic expressions for the equation. To apply a multiplier to any of the variables, change the value ahead of the wavelength/band.