Use Incidence Angle Image to generate incidence angle images from AIRSAR (excluding AIRSAR data associated with TOPSAR datasets), RADARSAT, SIR-C, and generic radar data. The incidence angles are calculated based on the near range and far range angles and assume flat topography.

  1. From the Toolbox, select one of the following:
    • Radar > AIRSAR > AIRSAR Incidence Angle Image
    • Radar > RADARSAT > RADARSAT Incidence Angle Image
    • Radar > SIR-C > SIR-C Incidence Angle Image
    • Radar > Generic Incidence Angle Image

      For SIR-C, AIRSAR, and RADARSAT, the Enter Filename dialog appears. For Generic, the Incidence Angle Parameters dialog appears (skip the next two steps).

  2. For SIR-C, AIRSAR, and RADARSAT-1 input files, select a file that contains the data acquisition parameters. For AIRSAR and RADARSAT-1, this information appears in the CEOS header. For RADARSAT-2, select an image file in GeoTIFF format (image_<n>.tif, one for each polarization channel).
  3. Click OK. The Incidence Angle Parameters dialog appears. For AIRSAR, RADARSAT, and SIR-C, ENVI reads the necessary information automatically from the header files. If all of the needed parameters are not found, enter the missing values in the corresponding fields.

    For generic input files, set the following parameters:

  4. Enter the number of output Samples and Lines and the near and far range angles, in degrees, in the corresponding fields.
    • Select the Near Range location from the corresponding radio buttons. The choices are Top, Bottom, Left, or Right.
    • Select Incidence Angle Units output in radians or degrees.
  5. Select output to File or Memory.
  6. Click OK.