# 4. Import signatures¶

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

## 4.1. Import library file¶

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¶

Import vector

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

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

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.