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Build SeaWiFS Geometry Files

Build SeaWiFS Geometry Files

Use Build SeaWiFS Geometry File to calculate the geometry for HDF and CEOS format LAC SeaWiFS data. When you select this procedure, ENVI extracts the header information and calculates the geometry values for each pixel. You can select which values to calculate: latitude, longitude, sensor azimuth and zenith angles, sun azimuth and zenith angles, and UTC time. The zenith angle is measured vertically from each pixel to the sensor or sun (straight above the pixel = 0 degrees) and the azimuth angle is the direction from each pixel to the sensor or sun with north = 0 degrees, and angles increasing clockwise (that is, east = 90 degrees).

Note: You can also georeference your SeaWiFS data by using the results from this procedure as the IGM input file in Georeferencing from Input Geometry.

  1. Open a SeaWiFS file as follows:
    • File > Open: Select a .hdf file.
    • File > Open As > Optical Sensors > SeaWiFS > CEOS: Open an image* file.
  2. Select Geometric Correction > Build Geometry File by Sensor > SeaWiFS CEOS Build Geometry File or SeaWiFS HDF Build Geometry File from the Toolbox. The SeaWiFS Input File dialog appears.
  3. Select an input file and perform optional spatial and spectral subsetting, then click OK.
  4. If your input file is not in HDF or CEOS format, select the associated HDF or CEOS annotation file to read the header information from.
  5. Click OK. The SeaWiFS Geometry Parameters dialog appears.
  6. Select the values to compute by selecting one of the following options:
    • To select individual values, select the check boxes next to the desired value.
    • To select a range of values, enter the beginning and ending numbers into the two fields next to the Add Range button and click Add Range.
    • To select all values, click Select All.
    • To de-select any selected items, click Clear.
  7. Select output to File or Memory.
  8. From the Output Data Type drop-down button, select Double or Floating Point.
  9. Click OK.



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