In Step 5 of the Target Detection Wizard, you can optionally perform an MNF transform on the input image. ENVI uses the MNF transform to segregate and equalize the noise in the data, and to reduce the data dimensionality for target detection processing. The resulting bands of the MNF transformed data are sorted by spatial coherence in descending order. Lower MNF bands typically have spatial structure and contain most of the information. Higher MNF bands typically have little spatial structure and contain most of the noise.

Note: If you choose not to apply the MNF transform, the Mixture Tuned Matched Filter (MTMF) and Mixture Tuned Target-Constrained Interference-Minimized Filter (MTTCIMF) target detection methods will not be available in the next step. MTMF and MTTCIMF perform Matched Filtering (MF) or Target-Constrained Interference-Minimized Filter (TCIMF) and add an infeasibility band to the results. The infeasibility band is used to reduce the number of false positives that are sometimes found when using MF or TCIMF alone

  1. To apply the MNF transform, leave the Apply MNF Transform? toggle at Yes. If you toggle to No, click Next to proceed.
  2. If you wish to set advanced parameters for MNF transformation, click Show Advanced Options. Otherwise, click Next to proceed. The next steps are for the advanced settings.
  3. To use only some of the MNF transformed bands in target detection processing, enter the Number of Selected MNF Bands.
  4. Note: It is recommended that you use the default number of bands to preserve the full data dimensionality.

  5. Click Noise Stats Shift Diff Spatial Subset to select a spatial subset or an area under an ROI/EVF or an image or file on which to calculate the statistics. You can then apply the calculated results to the entire file (or to the file subset, if you selected one when you selected the input file).
  6. Click Next in the Wizard. The Target Detection Methods panel appears.