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Bad Data Mitigation Tools

Bad Data Mitigation Tools

THOR includes several tools to reduce bad data in your input files, before starting a workflow.

Zero Bands


When you select a file for input into a workflow, THOR automatically detects if the file has bands that consist of all zeros. If it detects such a band, it appends a bad bands list to the header file.

You can also manually run this tool by selecting THOR > Tools > THOR Zero Bands from the Toolbox. Choose to output any bad bands to an optional Bad Bands List file (.txt), or output the good bands to a Good Bands List file (.txt). You can also select whether or not to append the bad bands list to the header file.

Spectral Smoothing


Select THOR > Tools > THOR Spectral Smoothing from the Toolbox.

This option uses the Savitsky-Golay smoothing filter to smooth noisy signals. For more information, see the SAVGOL description in IDL Help.

Set the Filter Width to the number of pixels to the left and right of the data point. Larger values produce a smoother result at the expense of flattening sharp peaks.

For smoothing, set the Order of the Derivative to 0 (default). To find the smoothed first derivative of the signal, set it to 1, for the second derivative, set it to 2, etc.

Typical values for Degree of Smoothing Polynomial are 2 to 4. Lower values will produce smoother results but may introduce bias. Higher values will reduce the filter bias, but may "over fit" the data and will give a noisier result. This value must be less than the Filter Width.

De-striping


Select THOR > Tools > THOR De-Striping from the Toolbox.

This option removes periodic scan line striping in image data. ENVI calculates the mean of every nth line or sample and normalizes each one to its respective mean. Use the toggle button to select between Vertical (Lines) or Horizontal (Rows) destriping.

Zero Pixel


Select THOR > Tools > THOR Zero Pixel from the Toolbox.

This option allows you to mask out pixel values of 0 in your data files. Select whether to perform masking on all bands, or on any band that contains pixel values of 0.

Spectral Binning


Select THOR > Tools > THOR Spectral Binning from the Toolbox.

This option allows you to divide spectral bands into bins, thus collecting the input band energy into the specified number of bins.



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