3.2. SCP dock

3.2.1. Simplified SCP dock

Simplified SCP dock

A Simplified interface is loaded after the first installation of the plugin. It is especially designed for new users in order to ease the classification process, from the definition of input images to executing the classification algorithm.

Astuce

The Complete interface can be loaded from the settings in the SCP menu, by deselecting Simplified interface and restarting QGIS.

SCP menu with activated option for the simplified interface

The SCP includes tools for downloading and preprocessing satellite images. The interface includes buttons for opening the following tools:

Download products	open the tab Download products
Image conversion	open the tab Preprocessing

3.2.1.1. Band set definition

Image input in SCP is named band set, and it is saved with the QGIS project. It is recommended to load single band raster in a Band set.

The section Band set definition includes the following tools:

Tool symbol and name	Description
Open file	open file explorer and add raster files (preferably single band raster) to the band set
Add layer	open a window to select single band rasters already loaded in QGIS and add them to the band set
Move up	move highlighted bands upward
Move down	move highlighted bands downward
Reset	clear all bands from band set
Delete row	remove highlighted bands from the band set
RGB=	select a Color Composite that is applied to the Band set (complete interface) and displayed in the map; new color composites can be entered typing the band numbers separated by - (e.g., RGB = 4-3-2); use the button to show/hide the band set in the map
Wavelength	rapid definition of band center wavelength for the following satellite sensors such as Band order (integer values), Landsat 8 OLI, Sentinel-2

Astuce

The Band set is also called active band set. The Complete interface allows for the creation of multiple band sets that can be used in other tools.

3.2.1.2. ROI & Signature list

ROIs are polygons used for the definition of the samples of land cover classes that are used by the classification algorithms. The SCP manages the ROIs by creating a file named Training input.

The Training input stores the ROI polygons and spectral signatures; depending on the algorithm, the training could be performed using ROI polygons (e.g., Random Forest) or spectral signatures (e.g., Spectral Angle Mapping). The Training input is displayed in QGIS as vector file.

Avertissement

In order to avoid data loss, do not edit the vector Training input using the QGIS tools. Use only the tools of SCP for managing the Training input.

SCP allows for the creation of temporary ROI polygons using a region growing algorithm or drawn manually with the tools provided in the Working toolbar (complete interface). These are temporary ROI polygons because the ROI creation is an interactive process, and one can refine the geometry according to photointerpreation. Then, one can save temporary ROI polygons in the Training input which is the actual input for classifications.

The Training input is composed of a vector part that stores the geometries and a spectral signature part, which are managed by SCP. A temporary layer is added to QGIS but the actual file is saved and modified during the editing in SCP.

The section ROI & Signature list includes the following tools:

Tool symbol and name	Description
Open file	open a training input file; ROIs and spectral signatures are loaded in ROI & Signature list; the vector part of the training input is loaded in QGIS
New file	create an empty training input file (.scpx); the vector part of the training input is loaded in QGIS; also a backup file is created (a file .scpx.backup in the same directory as the file .scpx) when the QGIS project is saved; to use the backup file simply rename it deleting the ending .backup extension and open it as training input
Training input	it displays the path to the training input file
Reset	remove the training input
Import file	open the tab Import signatures
Export ROIs	open the tab Export signatures and export highlighted items
Delete ROI	delete highlighted ROIs
Spectral plot	show the ROI spectral signature in the Spectral Signature Plot; spectral signature is calculated from the Band set (complete interface)
Spectral plot	activate the pointer to create a temporary ROI by drawing a polygon in the map; left click on the map to define the ROI vertices and right click to define the last vertex closing the polygon
Pointer	activate the pointer to create a temporary ROI using the region growing algorithm; left click on the map for creating the ROI
	undo of ROI creation from the Training input; it is possible to undo a maximum of 10 actions
	redo ROI creation in the Training input
Class	ROI class identifier
Name	ROI class name
Save	save the temporary ROI to the Training input using the defined classes and macroclasses; ROI is displayed in the ROI & Signature list

The tree list ROI & Signature list has the following fields:

• Class: Class value used for classification; it can be edited with a single click

• Name: Class Name; it can be edited with a single click

• Color: Class color; double click to select a color for the class that is used in the classification

3.2.1.3. Classification

In SCP, land cover classes (and ROIs) are defined with a system of Classes. Each Class is identified by a value and a Name, but only the Class value is used for the classification process.

The classification can be performed for the entire image (see Algorithm) or for a part of it creating a Classification preview.

The section Classification includes the following tools:

Tool symbol and name	Description
Algorithm	select a classification algorithm (additional parameters can be defined in Classification)
	activate the pointer for the creation of a Classification preview; left click the map to start the classification process and display the classification preview
RUN	select an output and run the classification

This tool allows for the selection of one the following classification algorithms:

• Maximum Likelihood

• Minimum Distance

• Multi-layer Perceptron

• Random Forest

• Spectral Angle Mapping

• Support Vector Machine

3.2.2. Complete interface

The Complete interface is designed for experienced users, and provides access to all the tools offered by the SCP. The Complete interface can be loaded from the settings in the SCP menu.

The Training input is composed of a vector part that stores the geometries and a spectral signature part, which are managed by SCP. A temporary layer is added to QGIS but the actual file is saved and modified during the editing in SCP.

In SCP, land cover classes (and ROIs) are defined with a system of Classes (Class ID) and Macroclasses (Macroclass ID) (see Classes and Macroclasses) that are used for the classification process; each Macroclass ID is related to a Macroclass Information (e.g. macroclass name) and each Class ID is related to a Class Information (e.g. class name), but only Macroclass ID and Class ID are used for the classification process.

The use of the Macroclass ID or Class ID for classifications is defined with the option Use MC ID or C ID in the Algorithm. Using Macroclass ID instead of Class ID is useful to group materials that belong to the same land cover class but have spectral signatures that are distant enough to be considered as different materials (e.g., different types of vegetation).

Spectral signatures of classes are calculated from the ROIs or can be imported from other sources (see Import signatures). It is worth pointing out that classification is always based on spectral signatures.

3.2.2.1. Home

Home

The left side of SCP dock contains buttons for accessing the main functions of SCP. The tab Home contains the buttons for accessing the main functions of SCP:

	Band set (complete interface)
	Basic tools
	Download products
	Preprocessing
	Band processing
	Postprocessing
	Band calc
	Script (complete interface)

3.2.2.1.1. SCP news

This section displays news about the SCP and related services. News are downloaded on startup (internet connection required). It can be enabled or disabled in the settings Settings.

3.2.2.2. Training input

Training input

This tool allows for the creation of the training input file (.scpx ) required for storing ROIs and spectral signatures. The training input file is created according to the characteristics of the active band set defined in Band set (complete interface). A new training input file should be created for every band set, unless the band sets have the same spectral characteristics and coordinate reference system.

Tool symbol and name	Description
	open a training input file; ROIs and spectral signatures are loaded in ROI & Signature list; the vector part of the training input is loaded in QGIS
	create an empty training input file (.scpx); the vector part of the training input is loaded in QGIS; also a backup file is created (a file .scpx.backup in the same directory as the file .scpx) when the QGIS project is saved; to use the backup file simply rename it deleting the ending .backup extension and open it as training input
Training input	it displays the path to the training input file
	remove the training input

The training input is displayed in QGIS as vector file. ROIs and spectral signatures are displayed in the ROI & Signature list.

Avertissement

In order to avoid data loss, do not edit the vector Training input using the QGIS tools. Use only the tools of SCP for managing the Training input.

3.2.2.2.1. ROI & Signature list

The tab ROI & Signature list displays the ROI polygons and spectral signatures contained in the training input file. The tab ROI & Signature list is structured as tree list, where every ROI is grouped in the corresponding Macroclass.

A filter for names can be defined in Filter .

The tree list ROI & Signature list has the following fields:

• MC ID: Macroclass ID is the root of corresponding ROIs and signatures; it can be edited with a single click; if the ID of a spectral signature is set 0, then pixels belonging to this signature are labelled as unclassified; every listed ROIs or signatures has a selection checkbox (only the spectral signatures checked in this list are used for the classification process);

• C ID: Class ID; it can be edited with a single click;

• Name: Macroclass and Class Name; it can be edited with a single click;

• Type: type of the item:

  • R = only ROI polygon;

  • S = only spectral signature;

  • RS = both ROI and spectral signature;

• Color: C ID color; double click to select a color for the class that is used in the classification;

Changes in the ROI & Signature list are applied to the file Training input only when the QGIS project is saved (but there is also the option Autosave). ROIs can be edited, deleted and merged from this list.

ROI & Signature list example

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According to Algorithm, classifications performed using C ID have the colors defined for classes in the ROI & Signature list; classifications performed using MC ID have the colors defined for the macroclasses.

If an item is a ROI polygon, double click the item to zoom to that ROI in the map. Items in the list can be highlighted with the mouse left click.

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ROIs and spectral signatures can be imported from other sources (see Import signatures) and exported (see Export signatures).

The following tools are available:

Tool symbol and name	Description
	merge highlighted spectral signatures or ROIs obtaining a new signature calculated as the average of signature values for each band (covariance matrix is excluded)
	calculate spectral signatures of highlighted ROIs using the active band set in Band set (complete interface)
	delete highlighted ROIs and signatures
	show the ROI spectral signature in the Spectral Signature Plot; spectral signature is calculated from the Band set (complete interface)
	add highlighted ROIs to the Scatter Plot
	open the tab Import signatures
	open the tab Export signatures and export highlighted items

ROI & Signature list is complementary to the Working toolbar (complete interface) and it allows for saving ROIs to the Training input defining classes and macroclasses. A Band set (complete interface) must be defined before the ROI creation, and ROI polygons must be inside the area of the Band set.

Tool symbol and name	Description
MC ID	ROI Macroclass ID
MC Name	ROI Macroclass Name
C ID	ROI Class ID
C Name	ROI Class Name
	undo of ROI creation from the Training input; it is possible to undo a maximum of 10 actions
	redo ROI creation in the Training input
Autosave	if checked, automatically save the ROI & Signature list to the Training input every time a ROI is saved
Signature	if checked, while saving a ROI, the spectral signature thereof is calculated (from Band set (complete interface) pixels under ROI polygon) and saved to Training input (calculation time depends on the band number of the active band set in Band set (complete interface))
	save the temporary ROI to the Training input using the defined classes and macroclasses; ROI is displayed in the ROI & Signature list

3.2.2.2.2. Right click menu

Right click menu

A right click on ROI & Signature list allows for opening a menu containing several functions to manage ROIs and spectral signatures.

Tool symbol and name	Description
Zoom to	zoom to highlighted items (if ROI polygons) in the map
Check/uncheck	check or uncheck highlighted items
Clear selection	clear selection of highlighted items
Collapse/expand all	collapse or expand all macroclasses
Change MC ID	edit the macroclass of highlighted items (using the value MC ID displayed in ROI & Signature list); if a macroclass is selected, the function is performed to all the included items
Change color	select a color for the highlighted items; if a macroclass is selected, the function is performed to all the included items
Merge items	merge highlighted spectral signatures or ROIs obtaining a new signature calculated as the average of signature values for each band (covariance matrix is excluded); if a macroclass is selected, the function is performed to all the included items
Calculate signatures	calculate spectral signatures of highlighted ROIs using the active band set in Band set (complete interface); if a macroclass is selected, the function is performed to all the included items
Delete items	delete highlighted ROIs and signatures; if a macroclass is selected, the function is performed to all the included items;
Add to spectral plot	show the ROI spectral signature in the Spectral Signature Plot; spectral signature is calculated from the Band set (complete interface); if a macroclass is selected, the function is performed to all the included items
Add to scatter plot	add highlighted ROIs to the Scatter Plot; if a macroclass is selected, the function is performed to all the included items
Properties	show the properties of highlighted items;
Import	open the tab Import signatures
Export	open the tab Export signatures and export highlighted items

3.2.2.3. ROI options

ROI options

ROI options are useful for displaying pixel values or improving the creation of ROIs.

Tool symbol and name	Description
Display	if the ROI creation pointer is active (see Working toolbar (complete interface)), the pixel value of selected vegetation index is displayed on the map; vegetation indices available in the combo box are: NDVI (Normalized Difference Vegetation Index); EVI (Enhanced Vegetation Index); Custom (use the custom expression defined in the following line)
	set a custom expression; expression is based on the Band set and bands such as band 1 is referred to as « b1 », band 2 as « b2 » and so on; also reference to band names such as « #NIR# » or « #RED# » can be used
Rapid ROI b.	if checked, temporary ROI is created with region growing using only one Band set (complete interface) band (i.e.region growing is rapider); the band is defined by the Band set number; if unchecked, ROI is the result of the intersection between ROIs calculated on every band (i.e. region growing is slower, but ROI is spectrally homogeneous in every band)
Auto-plot	calculate automatically the temporary ROI spectral signature and display it in the Spectral Signature Plot (MC Name of this spectral signature is set tempo_ROI)
Auto-refresh ROI	calculate automatically a new temporary ROI while Region growing parameters in the Working toolbar (complete interface) are being changed
Maximum training buffer	defines the maximum number of action for undo and redo ROIs; the higher is the number, the more is the required memory