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ENVI

Radar Backscatter

Radar Backscatter

Use Radar Backscatter to calibrate a radar amplitude raster to sigma nought backscatter, in decibels. It currently works with ALOS-1 or ALOS-2 PALSAR Level-1.1, 1.5, 2.1, and 3.1 data.

You can also write a script to perform backscatter calibration using ENVIRadarBackscatterTask.

For ALOS-2 Level-1.5, 2.1, and 3.1 data, sigma nought is calculated as follows:

For ALOS-2 Level-1.1 data, sigma nought is calculated as follows:

Where:

  • I is the imaginary part of the value
  • Q is the real part of the value
  • calibration factor is obtained from the ALOS metadata
  • DN refers to a single pixel value

ENVI calculates sigma nought on a pixel-by-pixel basis without any ensemble-based averaging.

Reference: Japanese Aerospace Exploration Agency (JAXA), ALOS-2/PALSAR-2 Level 1.1/1.5/3.1 CEOS SAR Product Format Description, May 23, 2014.

Follow these steps:

  1. From the Toolbox, select Radar > ALOS PALSAR > Radar Backscatter.
  2. Select an ALOS PALSAR amplitude raster and perform any optional spatial subsetting, then click OK.
  3. To write the output to disk, select the File radio button and specify a filename and location. To produce output in memory only, select the Virtual radio button.

  4. Enable the Preview check box to see a preview of the settings before you click OK to process the data. The preview is calculated only on the area in the Image window and uses the resolution level at which you are viewing the image. See Preview for details on the results.
  5. Enable the Display result check box to display the aggregated classification raster in the Image window when processing is complete. Otherwise, if the check box is disabled, the raster can be loaded from the Data Manager.
  6. Click OK.

 



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