3.2. SCP dock

The SCP dock allows for the the creation of ROIs (Regions Of Interest) and spectral signatures required for the classification of a Band set. The Training input, created with SCP, stores the ROI polygons and spectral signatures used for the land cover classification (see Tutorial 1: Your First Land Cover Classification).

ROIs are polygons used for the definition of the spectral characteristics of land cover classes. 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.

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. Temporary ROI polygons can be saved in the Training input along with the spectral signatures of the ROI.

The Training input is composed of a vector part (i.e. a shapefile) and a spectral signature part which are independent. The attribute table of the vector contains four fields as in the following table.

Training input fields
Description Field name Field type
Macroclass ID MC_ID int
Macroclass Name MC_info string
Class ID C_ID int
Class Name C_info string
TIP: The Training input is managed by SCP, a temporary layer is added to QGIS but the real 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. It is worth highlighting that when using Macroclass ID all the spectral signatures are evaluated separately and each pixel is classified with the corresponding MC ID (i.e. there is no combination of signatures before the classification).

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

The SCP dock contains the following tabs:

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

3.2.1. Home

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Home

The tab Home contains the buttons for accessing the main functions of SCP:

3.2.1.1. 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 Dock.

It also contains the following buttons:

  • User manual: open the link to the user manual;
  • Ask a question: open the link to the online help;
  • Support the SCP: open the link to support the SCP ;

3.2.2. Training input

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Training input

This tool allows for the creation of the training input file (.scp ) 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. 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.

  • 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 (.scp); the vector part of the training input is loaded in QGIS; also a backup file is created (a file .scp.backup in the same directory as the file .scp) 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 input_text project_save: it displays the path to the training input file;
  • reset: 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.

WARNING: 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.

3.2.2.1. 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.

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ROI & Signature list example

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 checkbox Autosave). ROIs can be edited, deleted and merged from this list.

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.

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

  • Filter input_text: set a filter for names;

  • input_table ROI & Signature list:
    • 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; if the ID of a spectral signature is set 0, then pixels belonging to this signature are labelled as unclassified;

    TIP: 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.

  • merge_sign: merge highlighted spectral signatures or ROIs obtaining a new signature calculated as the average of signature values for each band (covariance matrix is excluded);

  • add_sign_tool: calculate spectral signatures of highlighted ROIs using the active band set in Band set;

  • delete_signature: delete highlighted ROIs and signatures;

  • sign_plot: show the ROI spectral signature in the Spectral Signature Plot; spectral signature is calculated from the Band set;

  • scatter_plot : add highlighted ROIs to the Scatter Plot;

  • import_spectral_library: open the tab Import signatures;

  • export_spectral_library: open the tab Export signatures and export highlighted items;

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

  • MC ID input_number project_save: ROI Macroclass ID;
  • MC Name input_text project_save: ROI Macroclass Name;
  • C ID input_number project_save: ROI Class ID;
  • C Name input_text project_save: ROI Class Name;
  • undo_save_roi: delete the last saved ROI from the Training input;
  • checkbox Autosave project_save: if checked, automatically save the ROI & Signature list to the Training input every time a ROI is saved;
  • checkbox Signature project_save: if checked, while saving a ROI, the spectral signature thereof is calculated (from Band set pixels under ROI polygon) and saved to Training input (calculation time depends on the band number of the active band set in Band set);
  • save_roi: save the temporary ROI to the Training input using the defined classes and macroclasses; ROI is displayed in the ROI & Signature list;

3.2.2.1.1. Right click menu

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Right click menu

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

  • zoom_to_ROI Zoom to: zoom to highlighted items (if ROI polygons) in the map;
  • check Check/uncheck: check or uncheck highlighted items;
  • select_all Clear selection: clear selection of highlighted items;
  • docks Collapse/expand all: collapse or expand all macroclasses;
  • enter Change MC ID: edit the macroclass of highlighted items (using the value MC ID input_number displayed in ROI & Signature list); if a macroclass is selected, the function is performed to all the included items;
  • enter Change color: select a color for the highlighted items; if a macroclass is selected, the function is performed to all the included items;
  • merge_sign 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;
  • add_sign_tool Calculate signatures: calculate spectral signatures of highlighted ROIs using the active band set in Band set; if a macroclass is selected, the function is performed to all the included items;
  • delete_signature Delete items: delete highlighted ROIs and signatures; if a macroclass is selected, the function is performed to all the included items;
  • sign_plot Add to spectral plot: show the ROI spectral signature in the Spectral Signature Plot; spectral signature is calculated from the Band set; if a macroclass is selected, the function is performed to all the included items;
  • scatter_plot 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;
  • accuracy_tool Properties: show the properties of highlighted items;
  • import_spectral_library Import: open the tab Import signatures;
  • export_spectral_library Export: open the tab Export signatures and export highlighted items;

3.2.3. ROI options

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ROI options

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

  • checkbox Display input_list project_save: if the ROI creation pointer is active (see Working toolbar), 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); NDVI requires the near-infrared and red bands;
    • EVI (Enhanced Vegetation Index); EVI requires the blue, near-infrared and red bands converted to reflectance; wavelengths must be defined in the Band set;
    • Custom; use the custom expression defined in the following line;
    • input_text project_save: set a custom expression; expression is based on the Band set; bands are defined as bandset#b + band number (e.g. bandset#b1 for the first band of the Band set); for example NDVI for a Landsat image would be ( bandset#b4 - bandset#b3 ) / ( bandset#b4 + bandset#b3 );
  • checkbox Rapid ROI b. input_number project_save: if checked, temporary ROI is created with region growing using only one Band set 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);
  • radiobutton 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);
  • radiobutton Auto-refresh ROI: calculate automatically a new temporary ROI while Region growing parameters in the Working toolbar are being changed;