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ENVI

Synthesize SIR-C Data

Synthesize SIR-C Data

Synthesize SIR-C Data


SIR-C Single Look Complex (SLC) and Multi-Look Complex (MLC) images must be synthesized before you can use them in ENVI processing routines. Use Synthesize SIR-C Images to synthesize standard and specific send and receive polarization and total power (TP) images from SIR-C compressed scattering matrix files.

The input SIR-C data must be in ENVI compressed data product format (SIR-C standard file extension .cdp). For easier processing, name the files with the following convention: filename_c.cdp and filename_l.cdp.

If your data are Multi-Look Detected (MLD), these are just 2-byte integer data and do not need to be synthesized.

For other data types,use the View CEOS Header tool to determine the number of lines, samples, and offset for the image. Then, open the image by selecting File > Open As > Radar Sensors > sensor_type from the menu bar, and enter this information into the Edit Raster Metadata dialog that appears. (For complex data, be sure to set the Strip Line Header? toggle button to Yes.)

See the following sections:

Workflow


Follow these steps to synthesize SIR-C data:

  1. From the Toolbox, select Radar > SIR-C > Synthesize SIR-C Data.
  2. The Input Data Products Files dialog appears. Use this dialog to read the SIR-C compressed scattering matrix files.

    Note: Do not open the Stokes matrix files using the File menu selection from the Toolbox.

  3. Click Open File. The Enter Filename dialog appears.
  4. Select a SIR-C scattering matrix (.cdp) filename. If the file is a valid ENVI compressed data file with all of the required parameters, ENVI adds it to one of the Selected Files fields in the Input Data Product Files dialog (depending on whether the file is P-, L-, or C-band data). If you followed the suggested file naming convention described previously, ENVI automatically adds the correct filenames for the other two files to the appropriate fields. Otherwise, repeat the file selection process for each of the bands.
  5. If the input file is not a valid ENVI compressed data file, the SIR-C Header Parameters dialog appears. Enter any missing parameters.

  6. Click OK. The Synthesize Parameters dialog appears.
  7. Set the synthesizing parameters.
  8. Select output to File or Memory.
  9. Click OK. All synthesized bands are placed in a single output file. ENVI adds the resulting output to the Layer Manager.

Enter Missing SIR-C Parameters


If the SIR-C Header Parameters dialog appears when you select an input file, it means that information is missing from the header. All of the known parameters are listed in the dialog.

  1. Enter the number of Samples and Lines in the corresponding fields.
  2. Enter the image size in the range direction (in kilometers) in the Width (km) field.
  3. Enter the scene size in the azimuth direction (in kilometers) in the Length (km) field.
  4. To skip any imbedded header and get to the beginning of the SIR-C data, enter the byte offset in the Offset field.
  5. Select the C or L band radio button.
  6. Select SAR Channel Type by clicking on a SIR-C data type toggle button.
  7. To strip line headers from the input data and exclude them from output image, select Yes.
  8. Click OK. The Input File dialog appears.

Use the CEOS Header Tool to Find Missing Information


You should have at least four files for your SIR-C data. The largest file is usually the data file, and the second largest is usually the SAR leader file.

  1. From the Toolbox, select Radar > Open/Prepare Radar File > View Generic CEOS Header. The Enter Compressed Data Products Filename dialog appears.
  2. Select the SAR leader file and click Open. The CEOS Header Report dialog appears.
  3. Note the Processed Scene Range value. Enter this value in the Width (km) field of the SIR-C Header Parameters dialog when you later synthesize the data.
  4. Note the Processed Scene Azimuth value. Enter this value in the Length (km) field of the SIR-C Header Parameters dialog when you later synthesize the data.
  5. Note the Producttype value. Select the appropriate SAR Channel Type radio button in the SIR-C Header Parameters dialog when you later synthesize the data.
  6. Close the CEOS Header Report dialog.
  7. From the Toolbox, select Radar > Open/Prepare Radar File > View Generic CEOS Header again. The Enter Compressed Data Products Filename dialog appears.
  8. Select the data file and click Open. The CEOS Header Report dialog appears.
  9. Note the NumberofSamples and NumberofLines values. Enter these values in the Samples and Lines fields of the SIR-C Header Parameters dialog when you later synthesize the data.
  10. Note the RecordInfo value. The last number in the array is the size of the image offset or embedded header. Enter this value in the Offset field of the SIR-C Header Parameters dialog when you later synthesize the data. If there are two fields labeled RecordInfo in the CEOS Header Report, then take the two large numbers at the end of these lines and add them to determine the image offset.
  11. Now that you have the information you need, synthesize the SIR-C images. When you enter information in the SIR-C Header Parameters dialog, be sure to click the Yes radio button next to Strip Line Header?



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