The tab 
:guilabel:`Import signatures` allows for
importing spectral signatures from various sources.
This tool allows for importing spectral signatures from various sources:
a previously saved :ref:`training_input` (.scpx 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 :ref:`band_set_tab`,
and added to the :ref:`ROI_list`;
| Tool symbol and name | Description |
|---|---|
:guilabel:`Select a file`  |
open a file to be imported in the :ref:`training_input` |
This tool allows for importing a vector (shapefile or geopackage), selecting the corresponding fields of the :ref:`training_input`.
| Tool symbol and name | Description |
|---|---|
| :guilabel:`Select a vector` |
open a vector |
:guilabel:`MC ID field`  |
select the vector field corresponding to MC ID |
| :guilabel:`MC Name field` |
select the vector field corresponding to MC Name |
| :guilabel:`C ID field` |
select the vector field corresponding to C ID |
| :guilabel:`C Name field` |
select the vector field corresponding to C Name |
 :guilabel:`Calculate sig.` |
if checked, the spectral signature is calculated while the ROI is saved to :ref:`training_input` |
:guilabel:`Import vector`  |
import all the vector polygons as ROIs in the :ref:`training_input` |
The tab :guilabel:`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.
| Tool symbol and name | Description |
|---|---|
| :guilabel:`Select a chapter` |
select one of the library chapters; after the selection, chapter libraries are shown in :guilabel:`Select a library` |
| :guilabel:`Select a library` |
select one of the libraries; the library description is displayed in the frame :guilabel:`Library description` |
| :guilabel:`Import spectral library` |
download the library and add the sampled spectral signature to the :ref:`ROI_list` using the parameters defined for class and macroclass; the library is automatically sampled according to the image band wavelengths defined in the :guilabel:`active band set` in :ref:`band_set_tab`, and added to the :ref:`ROI_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.