4. Import signatures

The tab import_spectral_library Import signatures allows for importing spectral signatures from various sources.

4.1. Import library file

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Import library file

This tool allows for importing spectral signatures from various sources: a previously saved Training input (.scp file); a USGS Spectral Library (.asc file); a previously exported CSV file. In case of USGS Spectral Library, the library is automatically sampled according to the image band wavelengths defined in the Band set, and added to the ROI & Signature list;

4.2. Import vector

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Import vector

This tool allows for importing a vector (shapefile or geopackage), selecting the corresponding fields of the Training input.

  • Select a vector open_file: open a vector;
  • MC ID field input_list: select the vector field corresponding to MC ID;
  • MC Name field input_list: select the vector field corresponding to MC Name;
  • C ID field input_list: select the vector field corresponding to C ID;
  • C Name field input_list: select the vector field corresponding to C Name;
  • checkbox Calculate sig.: if checked, the spectral signature is calculated while the ROI is saved to Training input;
  • Import vector enter: import all the vector polygons as ROIs in the Training input;

4.3. Download USGS Spectral Library

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Download USGS Spectral Library

The tab Download USGS Spectral Library allows for the download of the USGS spectral library (Clark, R.N., Swayze, G.A., Wise, R., Livo, E., Hoefen, T., Kokaly, R., Sutley, S.J., 2007, USGS digital spectral library splib06a: U.S. Geological Survey, Digital Data Series 231).

The libraries are grouped in chapters including Minerals, Mixtures, Coatings, Volatiles, Man-Made, Plants, Vegetation Communities, Mixtures with Vegetation, and Microorganisms. An internet connection is required.

  • Select a chapter input_list: select one of the library chapters; after the selection, chapter libraries are shown in Select a library;

  • Select a library input_list: select one of the libraries; the library description is displayed in the frame Library description;

  • Import spectral library enter: download the library and add the sampled spectral signature to the ROI & Signature list using the parameters defined for class and macroclass; the library is automatically sampled according to the image band wavelengths defined in the active band set in Band set, and added to the ROI & Signature list;

    TIP: Spectral libraries downloaded from the USGS Spectral Library can be used with Minimum Distance or Spectral Angle Mapping algorithms, but not Maximum Likelihood because this algorithm needs the covariance matrix that is not included in the spectral libraries.