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ENVI

Vegetation Suppression

Vegetation Suppression

Use Vegetation Suppression to remove the vegetation spectral signature from multispectral and hyperspectral imagery, using information from red and near-infrared bands. This method helps you better interpret geologic and urban features and works best with open-canopy vegetation in medium spatial resolution (30 m) imagery.

You can also write a script to perform vegetation suppression using the ENVIVegetationSuppressionTask routine.

The algorithm models the amount of vegetation per pixel using a vegetation transform. The model calculates the relationship of each input band with vegetation, then it decorrelates the vegetative component of the total signal on a pixel-by-pixel basis for each band. You can use the results of vegetation suppression for qualitative analysis, but not for subsequent spectral analysis.

Vegetation suppression is most commonly used in lithologic mapping and linear feature enhancement in areas with open canopies. For closed canopies in moderate-resolution data, vegetation suppression is primarily used for linear feature enhancement.

Reference

Crippen, R. E., and R. G. Blom. 2001. Unveiling the lithology of vegetated terrains in remotely sensed imagery. Photogrammetric Engineering & Remote Sensing, Vol. 67, No. 8, pp. 935-943.

  1. From the Toolbox, select Spectral > Vegetation > Vegetation Suppression. Input a multispectral file, and perform optional spatial or spectral subsetting. For spectral subsetting, you must select two or more bands.
    • If the associated header contains wavelength information, ENVI automatically determines the proper red and infrared bands to use for vegetation suppression. ENVI uses the band closest to 0.66 μm as the red band, and it uses the band closest to 0.83 μm as the near-infrared band.
    • If the header does not contain wavelength information, the Select Near Infrared Band dialog appears. Select the near-infrared band. Click OK. The Select Red Band dialog appears. Select the red band.
    • If the image file has wavelength information but does not have a near-infrared or red band, or if it has only one band, ENVI issues an error message and ends vegetation suppression.
  2. In the Select Output File Parameters, click the File or Memory button to output the result to file or memory. File output options include ENVI and TIFF/GeoTIFF and requires a filename.
  3. Select the Display Result check box to automatically display the output result in the Image window view. This check box overrides the Auto Display Files On Open preference. If you clear this check box, the output result does not automatically display after saving. ENVI remembers your last selection each subsequent time you create output.
  4. Click OK. The Process Manager shows the status of vegetation suppression processing. ENVI adds the output image to the Data Manager. The default preferences determine if it is added to the Layer Manager or not.



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