3.5. Spectral Signature Plot

The window Spectral Signature Plot includes several functions for displaying spectral signature values as a function of wavelength (defined in the Band set). Signatures can be added to the Spectral Signature Plot through the SCP dock.

Overlapping signatures (belonging to different classes or macroclasses) are highlighted in orange in the table Signature list; the overlapping check is performed considering MC ID or C ID according to the setting Use MC ID C ID in Classification. Overlapping signatures sharing the same ID are not highlighted.

_images/spectral_signature.png — Spectral Signature Plot

3.5.1. Signature list

The Signature list is a table that includes the spectral signatures added from the SCP dock.

S	MC ID	MC Name	C ID	C Name	Color
checkbox field; if checked, the spectral signature is displayed in the plot	signature Macroclass ID	signature Macroclass Name	signature Class ID	signature Class Name	signature color; also, the combination MC ID-C ID is displayed in case of overlap with other signatures

The following tools are available.

Tool symbol and name	Description
	remove highlighted signatures from this list
	add highlighted spectral signatures to ROI & Signature list
	calculate the spectral distances of spectral signatures displayed in the plot; distances are reported in the tab Spectral distances

3.5.1.1. Plot

Left click and hold inside the plot to move the view of the plot. Use the mouse wheel to zoom in and out the view of the plot. Right click and hold inside the plot to zoom in a specific area of the plot. Legend inside the plot can be moved using the mouse.

The following tools are available.

Tool symbol and name	Description
	automatically fit the plot to data
	save the plot image to file (available formats are `.jpg`, `.png`, and `.pdf`)
Plot value range	if checked, plot the value range for each signature with a semi-transparent area
Band lines	if checked, display a vertical line for each band (center wavelength)
Grid	if checked, display a grid
Max characters	set the maximum length of text in the legend
x y	display x y coordinates of mouse cursor inside the plot

_images/example_signature.png — Spectral Signature: Example of plot

3.5.1.2. Signature details

Display the details about spectral signatures (i.e. Wavelength, Values, and Standard deviation). In case of signatures calculated from ROIs, the ROI size (number of pixels) is also displayed.

_images/example_details.png — Spectral Signature: Example of signature details

3.5.1.3. Spectral distances

Display spectral distances of signatures (see Signature list), which are useful for assessing ROI separability (see Spectral Distance).

The following spectral distances are calculated :

Spectral Angle: range [0 = identical, 90 = different]; useful in particular for Spectral Angle Mapping classifications
Euclidean Distance: useful in particular for Minimum Distance classifications
Bray-Curtis Similarity: range [0 = different, 100 = identical]; useful in general

Values are displayed in red if signatures are particularly similar.

_images/example_distance.png — Spectral Signature: Example of spectral distances