6. Multiple ROI Creation

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roi_multiple Multiple ROI Creation

This tab allows for the automatic creation of ROIs, useful for the rapid classification of multi-temporal images, or for accuracy assessment. Given a list of point coordinates and ROI options, this tool performs the region growing of ROIs. Created ROIs are automatically saved to the Training input. The active band set in Band set is used for calculations.

6.1. Create random points

  • Number of points input_number: set a number of points that will be created when Create points enter is clicked;
  • checkbox inside grid input_number: if checked, the band set area is divided in cells where the size thereof is defined in the combobox (image unit, usually meters); points defined in Number of random points are created randomly within each cell;
  • checkbox min distance input_number: if checked, random points have a minimum distance defined in the combobox (image unit, usually meters); setting a minimum distance can result in fewer points than the number defined in Number of points;
  • Create points enter: create random points inside the band set area;
  • checkbox stratified for the values input_text of the first band of the band set min distance input_number: if checked, create random points inside the values defined in the expression calculated for the first band of the defined band set; the expression must include the variable raster ; multiple expressions can be entered separated by semicolon ( ; ) but the total number of stratified points is the same as the defined Number of points;

6.2. Point coordinates and ROI definition

  • input_table Point coordinates and ROI definition: table containing the following fields;
    • X : point X coordinate (float);
    • Y : point Y coordinate (float);
    • MC ID: ROI Macroclass ID (int);
    • MC Name: ROI Macroclass Name (text);
    • C ID: ROI Class ID (int);
    • C Name: ROI Class Name (text);
    • Min : the minimum area of a ROI (in pixel unit);
    • Max : the maximum width of a ROI (in pixel unit);
    • Dist : the interval which defines the maximum spectral distance between the seed pixel and the surrounding pixels (in radiometry unit);
    • Rapid ROI band : if a band number is defined, ROI is created only using the selected band, similarly to Rapid ROI band in ROI & Signature list ;
  • add: add a new row to the table; all the table fields must be filled for the ROI creation;
  • remove: delete the highlighted rows from the table;
  • import: import a point list from text file or a point shapefile to the table; in case of text file, every line must contain values separated by tabs of X, Y, MC ID, MC Name, Class ID, C Name, Min, Max, Dist, and optionally the Rapid ROI band; in case of shapefile, only point coordinates are imported;
  • export: export the point list to text file;
  • checkbox Calculate sig.: if checked, the spectral signature is calculated while the ROI is saved to Training input;
  • RUN run: start the ROI creation process for all the points and save ROIs to the Training input;