Enhance a multispectral image by merging it with a higher resolution panchromatic image to produce a high resolution color image. In this workflow, the Brovey Transform is used to merge two images.
The Brovey Transform was developed to visually increase contrast in the low and high ends of an image's histogram (that is, to provide contrast in shadows, water and high reflectance areas such as urban features). Consequently, the Brovey Transform should not be used if preserving the original scene radiometry is important. However, it is good for producing RGB images with a higher degree of contrast in the low and high ends of the image histogram and for producing "visually appealing" images.
Since the Brovey Transform is intended to produce RGB images, only three bands at a time should be merged from the input multispectral scene, such as bands 3,2,1 from a SPOT or Landsat TM image or 4,3,2 from a Landsat TM image. The resulting merged image should then be displayed with bands 1,2,3 to RGB.
The images in this workflow are subsets of images provided courtesy of GIS Department, Cherokee County, Georgia.
Geographic, WGS 84
5.50 x 6.65 meters
Geographic, WGS 84
Multispectral Image, Panchromatic Image, and Merged Result
Specify Input Images and Output Image
- Click Raster tab > Pan Sharpen > Resolution Merge.
The Resolution Merge dialog opens.
- In the High Resolution Input File field, click to open a File Selector. Navigate to your high resolution panchromatic image and select it.
- In the Multispectral Input File field, click to open a File Selector. Navigate to your lower resolution multispectral image and select it.
In this example, the Number of layers for the multispectral image is 7.
- In the Output File field, click to open a File Selector and navigate to the directory to store the output file.
- Click the Files of type field to select one of the raster file formats for the output file.
In this example, the image files sizes are quite large, therefore the output image was compressed to avoid creating a very large output image.
- Enter a name for the output file such as merge_brovey.jp2.
Specify Merge Method and Other Options
- In Method, click Brovey Transform.
- In Output Options, click the checkbox for Ignore Zero in Stats.
- In the Layer Selection field, use 3,2,1 in the Select Layers field. In this workflow, the multispectral image was captured from Landsat 5 TM sensor. Since the Brovey Transform is intended to produce RGB images, only three bands at a time should be merged from the input multispectral scene, such as bands 3,2,1 from a SPOT or Landsat TM image or 4,3,2 from a Landsat TM image.
- Set Data Type to the same raster data type as the input images.
- Leave Resampling Techniques at its default setting.
- Click OK.
The Process List dialog reports the status of the job. Close the dialog when finished.
- Open all three images in individual 2D Views and compare. See Multispectral Image, Panchromatic Image, and Merged Result graphic as an example.
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