Use SIR-C Multilook to reduce speckle noise in SAR data and to multilook SIR-C data on disk to a specified number of looks, number of lines and samples, or azimuth and range resolutions.

The data to multilook must be compressed data.

  1. From the Toolbox, select Radar > SIR-C > SIR-C Multi-Look. The Input Data Product Files dialog appears.
  2. Select a compressed input file. The SIRC Multi-Look Parameters dialog appears.
  3. Choose the files to multilook by from the Select Files to Multilook list.
  4. Enter the number of looks in the Samples (range) and Lines (az) directions or select from the following options.
    • To specify the number of pixels in the output image, enter the values in the Pixels fields for the samples and lines.
    • To specify the output pixel size in meters, enter the values in the Pixel Size (m) fields for samples and lines.
  5. When you enter a value for one of the parameters, ENVI automatically calculates the others to match. For example, if you enter the Pixel Size as 30 m, then ENVI calculates the corresponding number of pixels and the looks and changes them in the corresponding fields.

    ENVI supports both integer and floating-point number.

  6. Perform optional spatial subsetting by clicking Spatial Subset.
  7. Enter a base name in the Enter Base Filename field. ENVI uses this value as the basis for multiple filenames, one for each frequency selected. For example if you enter sirc as the base name and both C-band and L-band data are being processed, then ENVI creates two output files named sirc_c.cdp and sirc_l.cdp
  8. Click OK.

Use the synthesize function to generate image data from the output multilooked compressed data files.