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wxGUI GCP Manager

DESCRIPTION

       The  GCP  Manager  is  a wxGUI extension which allows the user to create, edit, and manage
       Ground Control Points. It is available  from  the  menu  "File  |  Manage  Ground  Control
       Points".

       The  GCP  Manager provides an interactive graphical interface to manage and analyze Ground
       Control Points. A backup copy of the initial POINTS file is always maintained and  updated
       only  on  request  (Save GCPs to POINTS file). This guarantees that accidental changes are
       not permanent and can be undone by reloading the Ground Control Points.

       The GCP Manager must be started in the target location, not in the source location.

       The GCP Manager is structured into three panels:

           ·   The topmost panel shows a list of Ground Control Points. Tools to  manipulate  and
               analyze  GCPs  are provided in the toolbar. This panel can be moved out of the GCP
               manager window by either dragging with the caption  or  by  clicking  on  the  pin
               button  on  the right in the caption.  This panel can also be placed below the map
               displays by dragging.

           ·   The two panels in the lower part are used for map and GCP display, the  left  pane
               showing  a map from the source location and the right pane showing a reference map
               from the target location. Numbered Ground Control Points are  shown  on  both  map
               displays.

   Components of the GCP Manager
       Toolbars

       Two  toolbars are provided with the GCP Manager, one for managing the map displays and one
       for managing the GCP list.

       List of ground control points

       The list of Ground Control Points can be sorted by clicking on a column  header.  Clicking
       on  a  cloumn  header will sort the GCPs ascending, a second click on the same column will
       sort the GCPs descending. Overall RMS error and individual RMS errors of  all  points  are
       often  improved  if the GCP with the highest RMS error is adjusted. Individual coordinates
       can be edited by double-clicking on a row.

       The first column holds a checkbox and displays the point number. A GCP is  only  used  for
       RMS error calculation and georectification if its checkbox on the left is checked. Uncheck
       to deactivate a GCP (mark as unused GCP).

       Two panels for map display

       The left panel is used to display a map from the  source  location,  the  right  panel  to
       display  a  map  from  the target loaction. Zooming in and out is always possible with the
       mouse wheel and done for each map canvas separately.

       GCPs are displayed in different colors, depending on whether a GCP has a high  RMS  error,
       is  currently  unused  or is currently selected. Optionally, currently unused GCPs are not
       shown on the map display.

       Statusbar

       At the bottom of the GCP Manager is a statusbar providing several functions.  The  default
       is  set  to  Go  to GCP No. (see also below).  Typing a number or using the up/down arrows
       will center the maps on the given GCP, useful with a high zoom.

   GCP Map Display Toolbar
           Display map
           Displays maps for source and target canvas and re-renders any layers that have changed
           since the last time the display was updated.

           Re-render map
           Re-renders  both  source  and target canvas regardless of whether they have changed or
           not.

           Erase display
           Erases both source and target canvas to a white background.

           Define GCP (Ground Control Points)
           On left mouse click, coordinates are defined for the currently selected GCP.

           Pan
           Interactive selection of a new center of view in the active display monitor. Drag  the
           pan  cursor  while  pressing the left mouse button to pan. Alternatively left-click on
           the new center. Panning changes the location of the region displayed but not the  size
           of the area displayed or the resolution.

           Zoom in
           Interactive  zooming  with  the  mouse  in  the  active map canvas (source or target).
           Drawing a box or just a left click with  the  mouse  and  zoom-in  cursor  causes  the
           display  to  zoom  in  so  that the area defined by the box fills the display. The map
           resolution is not changed. Clicking with the zoom-in cursor causes the display to zoom
           in  by  30%,  centered  on  the  point where the mouse is clicked. Zooming changes the
           display region extents (both size and location of area displayed).

           Zoom out
           Interactive zooming with the mouse in  the  active  map  canvas  (source  or  target).
           Drawing  a  box  or  just  a  left click with the mouse and zoom-out cursor causes the
           display to zoom out so that the area displayed shrinks to fill the area defined by the
           box.  The  map resolution is not changed. Clicking with the zoom-out cursor causes the
           display to zoom out by 30%, centered on the point where the mouse is clicked.  Zooming
           changes the display region extents (both size and location of area displayed).

           Adjust display zoom
           Source  and  target  display  are  adjusted  by  using the current GCPs for coordinate
           transformation:

       Adjust source display to target display
           The extents of the source display are adjusted to the current extents  of  the  target
           display.

       Adjust target display to source display
           The  extents  of  the source display are adjusted to the current extents of the target
           display.

       Set active map canvas
           Sets the currently active map canvas (source or  target).  Click  to  set  active  map
           canvas  for  Return  to  previous  zoom  or Zoom to extent of currently displayed map.
           Alternatively, move the mouse over the map canvas to be used as active canvas.

           Return to previous zoom
           Returns to the previous zoom extent. Up to 10 levels of zoom back are maintained.

         Zoom to extent of currently displayed map
           Zoom to the extent of the currently displayed map in the active map canvas (source  or
           target).

         Settings
           Shows a settings dialog for GCP management and display:

       Symbology
           Settings for map and GCP display:

       Highlight highest RMS error only
           Only  the GCP with the highest RMS error will be displayed in a different colour, both
           in the list of GCPs and the GCP Map Display.

       Factor for RMS error threshold = M + SD * factor:
           All GCPs with an RMS error larger than mean RMS + RMS standard deviation * this factor
           will  be  displayed  in  a  different colour, both in the list of GCPs and the GCP Map
           Display. As a rule of thumb, GCPs with an RMS error larger than M + SD *  2  are  most
           probably  wrong.  GCPs  with  an  RMS  error  larger  than M + SD * 1 are worth closer
           inspection. This option is only available if  Highlight  highest  RMS  error  only  is
           unchecked.

       Color
           Set the color for GCPs on the GCP Map Display.

       Color for high RMS error
           Set the color for GCPs with a high RMS error on the GCP Map Display.

       Color for selected GCP
           Set the color for the currently selected GCP on the GCP Map Display.

       Show unused GCPs
           If unchecked, unused GCPs will not be shown on the GCP Map Display.

       Color for unused GCPs
           Set the color for unused GCPs on the GCP Map Display.

       Symbol size
           Set the symbol size for GCPs on the GCP Map Display.

       Line width
           Set the line width for GCPs on the GCP Map Display.

       Select source map to display
           Select a source map for the left pane of the GCP Map Display.

       Select target map to display
           Select a target map for the right pane of the GCP Map Display.

       Rectification
           Settings for georectification:

       Select rectification method
           Set  the  polynomial  order for georectification. This order will also be used for RMS
           error calculation.

       Clip to computational region in target location
           Clip raster maps to the current computational  region  in  the  target  location  when
           georectifying.

       Extension for output maps
           Change the extension for output map names when doing the actual georectification.

         Show Help
           Show help page for the GCP Manager.

         Quit
           Quit the GCP Manager.

   Toolbar for the GCP list
         Save GCPs to POINTS file
           The  current  list of GCPs is saved to the imagery group’s POINTS file and to a backup
           copy.

         Add new GCP
           Adds a new Ground Control Point to the list and selects it for editing.

         Delete selected GCP
           Deletes the currently selected GCP from the list.

         Clear selected GCP
           Resets all coordinates of the currently selected GCP to 0 (zero).

         Reload GCPs from POINTS file
           Reloads GCPs from the imagery group’s POINTS file.

         Recalculate RMS error
           Recalculates forward and backward RMS error for all  GCP  marked  for  use  (activated
           checkbox in first row).

         Georectify
           Uses i.rectify to georectify all images in the source imagery group.

   GCP Map Display Statusbar
       The  GCP  map  display  statusbar is similar to the statusbar in the regular GRASS GIS map
       display with two differences, Go to has been replaced with Go to GCP  No.  and  Projection
       has been replaced with RMS error.

       If  Go to GCP No. is selected, a GCP number can be given in the left side of the statusbar
       and the source and target map canvas will be centered on the given GCP.  Clicking  on  the
       map canvas will update coordinates for this GCP.

       If RMS error is selected, the overall forward and backward RMS error is displayed.

SEE ALSO

        wxGUI
       wxGUI components

        i.rectify, m.transform, v.rectify

       See also video tutorials on GRASS Wiki.

AUTHORS

       Markus Metz
       Based on the Georectifier (GRASS 6.4.0) by Michael Barton
       Martin Landa, Czech Technical University in Prague, Czech Republic

       $Date: 2017-11-03 18:21:39 +0100 (Fri, 03 Nov 2017) $

SOURCE CODE

       Available at: wxGUI GCP Manager source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual