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Remove Antenna Gain Variations

Remove Antenna Gain Variations

Radar images typically have a variation in gain across the range direction due to the instrument’s antenna gain pattern. Use Antenna Pattern Correction to remove this gain variation. You can calculate and plot azimuth mean values to show the mean variation in the range direction. A polynomial function, with a user-defined order, is fit to the means and used to remove the gain variation. You can select either an additive or multiplicative correction.

Reference

Ulaby, F. T., R. K. Moore, and A. K. Fung, 1982. Microwave Remote Sensing Active and Passive, Volume II, Artech House, Inc., Norwood, MA, p.1064.

  1. From the Toolbox, select Radar > Antenna Pattern Correction. The Antenna Pattern Input File dialog appears.
  2. Select an input file and perform optional spatial and spectral subsetting and/or masking, then click OK. The Antenna Pattern Correction Parameters dialog and an Antenna Pattern Correction plot appear. The plot shows the mean data values in green with the selected polynomial fit overlaid in red. The following image shows an example:
  3. In the Antenna Pattern Correction Parameters dialog, select a Range Direction of Samples or Lines.
  4. Select a Correction Method of either Additive or Multiplicative. Typically, a multiplicative correction is used for radar antenna pattern variations.
  5. Enter the Polynomial Order and click Plot Polynomial. You can change the polynomial order and plot it again. It is best to use a low order polynomial so as not to remove the local variation in backscatter signal.
  6. The Antenna Pattern Correction plot menu bar is not active until you close the Antenna Pattern Correction Parameters dialog.

  7. Select output to File or Memory.
  8. Click OK.



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