1wxGUI.gcp(1)                  Grass User's Manual                 wxGUI.gcp(1)
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wxGUI GCP Manager

DESCRIPTION

7       The  GCP  Manager is a wxGUI extension which allows the user to create,
8       edit, and manage Ground Control Points. It is available from  the  menu
9       "File | Manage Ground Control Points".
10
11       The  GCP  Manager provides an interactive graphical interface to manage
12       and analyze Ground Control Points. A backup copy of the initial  POINTS
13       file  is  always  maintained  and updated only on request (Save GCPs to
14       POINTS file). This guarantees that accidental changes are not permanent
15       and can be undone by reloading the Ground Control Points.
16
17       The  GCP  Manager  must  be  started in the target location, not in the
18       source location.
19
20       The GCP Manager is structured into three panels:
21
22           ·   The topmost panel shows a list of Ground Control Points.  Tools
23               to  manipulate  and  analyze  GCPs are provided in the toolbar.
24               This panel can be moved out of the GCP manager window by either
25               dragging  with  the caption or by clicking on the pin button on
26               the right in the caption.  This panel can also be placed  below
27               the map displays by dragging.
28
29           ·   The  two panels in the lower part are used for map and GCP dis‐
30               play, the left pane showing a map from the source location  and
31               the  right  pane  showing a reference map from the target loca‐
32               tion. Numbered Ground Control Points are shown on both map dis‐
33               plays.
34
35   Components of the GCP Manager
36       Toolbars
37
38       Two  toolbars  are  provided with the GCP Manager, one for managing the
39       map displays and one for managing the GCP list.
40
41       List of ground control points
42
43       The list of Ground Control Points can be sorted by clicking on a column
44       header.  Clicking  on  a  cloumn header will sort the GCPs ascending, a
45       second click on the same column will sort the GCPs descending.  Overall
46       RMS error and individual RMS errors of all points are often improved if
47       the GCP with the highest RMS error is adjusted. Individual  coordinates
48       can be edited by double-clicking on a row.
49
50       The  first column holds a checkbox and displays the point number. A GCP
51       is only used for RMS error  calculation  and  georectification  if  its
52       checkbox  on  the left is checked. Uncheck to deactivate a GCP (mark as
53       unused GCP).
54
55       Two panels for map display
56
57       The left panel is used to display a map from the source  location,  the
58       right  panel  to display a map from the target loaction. Zooming in and
59       out is always possible with the mouse wheel and done for each map  can‐
60       vas separately.
61
62       GCPs  are displayed in different colors, depending on whether a GCP has
63       a high RMS error, is currently unused or is currently selected. Option‐
64       ally, currently unused GCPs are not shown on the map display.
65
66       Statusbar
67
68       At the bottom of the GCP Manager is a statusbar providing several func‐
69       tions. The default is set to Go to GCP No. (see also below).  Typing  a
70       number  or  using  the up/down arrows will center the maps on the given
71       GCP, useful with a high zoom.
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73   GCP Map Display Toolbar
74           Display map
75           Displays maps for source and target canvas and re-renders any  lay‐
76           ers that have changed since the last time the display was updated.
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78           Re-render map
79           Re-renders both source and target canvas regardless of whether they
80           have changed or not.
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82           Erase display
83           Erases both source and target canvas to a white background.
84
85           Define GCP (Ground Control Points)
86           On left mouse click, coordinates  are  defined  for  the  currently
87           selected GCP.
88
89           Pan
90           Interactive selection of a new center of view in the active display
91           monitor. Drag the pan cursor while pressing the left  mouse  button
92           to pan. Alternatively left-click on the new center. Panning changes
93           the location of the region displayed but not the size of  the  area
94           displayed or the resolution.
95
96           Zoom in
97           Interactive zooming with the mouse in the active map canvas (source
98           or target). Drawing a box or just a left click with the  mouse  and
99           zoom-in  cursor  causes  the  display  to  zoom in so that the area
100           defined by the box fills the display. The  map  resolution  is  not
101           changed.  Clicking  with  the  zoom-in cursor causes the display to
102           zoom in by 30%, centered on the point where the mouse  is  clicked.
103           Zooming  changes the display region extents (both size and location
104           of area displayed).
105
106           Zoom out
107           Interactive zooming with the mouse in the active map canvas (source
108           or  target).  Drawing a box or just a left click with the mouse and
109           zoom-out cursor causes the display to zoom out  so  that  the  area
110           displayed shrinks to fill the area defined by the box. The map res‐
111           olution is not changed. Clicking with the  zoom-out  cursor  causes
112           the  display  to  zoom  out by 30%, centered on the point where the
113           mouse is clicked. Zooming changes the display region extents  (both
114           size and location of area displayed).
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116           Adjust display zoom
117           Source  and  target  display are adjusted by using the current GCPs
118           for coordinate transformation:
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120       Adjust source display to target display
121           The extents of the source  display  are  adjusted  to  the  current
122           extents of the target display.
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124       Adjust target display to source display
125           The  extents  of  the  source  display  are adjusted to the current
126           extents of the target display.
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128       Set active map canvas
129           Sets the currently active map canvas (source or target).  Click  to
130           set active map canvas for Return to previous zoom or Zoom to extent
131           of currently displayed map. Alternatively, move the mouse over  the
132           map canvas to be used as active canvas.
133
134           Return to previous zoom
135           Returns  to  the previous zoom extent. Up to 10 levels of zoom back
136           are maintained.
137
138         Zoom to extent of currently displayed map
139           Zoom to the extent of the currently displayed map in the active map
140           canvas (source or target).
141
142         Settings
143           Shows a settings dialog for GCP management and display:
144
145       Symbology
146           Settings for map and GCP display:
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148       Highlight highest RMS error only
149           Only the GCP with the highest RMS error will be displayed in a dif‐
150           ferent colour, both in the list of GCPs and the GCP Map Display.
151
152       Factor for RMS error threshold = M + SD * factor:
153           All GCPs with an RMS error larger than  mean  RMS  +  RMS  standard
154           deviation  *  this  factor will be displayed in a different colour,
155           both in the list of GCPs and the GCP Map  Display.  As  a  rule  of
156           thumb, GCPs with an RMS error larger than M + SD * 2 are most prob‐
157           ably wrong. GCPs with an RMS error larger than M + SD * 1 are worth
158           closer inspection. This option is only available if Highlight high‐
159           est RMS error only is unchecked.
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161       Color
162           Set the color for GCPs on the GCP Map Display.
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164       Color for high RMS error
165           Set the color for GCPs with a high RMS error on the  GCP  Map  Dis‐
166           play.
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168       Color for selected GCP
169           Set  the  color  for the currently selected GCP on the GCP Map Dis‐
170           play.
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172       Show unused GCPs
173           If unchecked, unused GCPs will not be shown on the GCP Map Display.
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175       Color for unused GCPs
176           Set the color for unused GCPs on the GCP Map Display.
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178       Symbol size
179           Set the symbol size for GCPs on the GCP Map Display.
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181       Line width
182           Set the line width for GCPs on the GCP Map Display.
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184       Select source map to display
185           Select a source map for the left pane of the GCP Map Display.
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187       Select target map to display
188           Select a target map for the right pane of the GCP Map Display.
189
190       Rectification
191           Settings for georectification:
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193       Select rectification method
194           Set the polynomial order for georectification. This order will also
195           be used for RMS error calculation.
196
197       Clip to computational region in target location
198           Clip  raster maps to the current computational region in the target
199           location when georectifying.
200
201       Extension for output maps
202           Change the extension for output map names  when  doing  the  actual
203           georectification.
204
205         Show Help
206           Show help page for the GCP Manager.
207
208         Quit
209           Quit the GCP Manager.
210
211   Toolbar for the GCP list
212         Save GCPs to POINTS file
213           The  current  list  of  GCPs is saved to the imagery group’s POINTS
214           file and to a backup copy.
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216         Add new GCP
217           Adds a new Ground Control Point to the  list  and  selects  it  for
218           editing.
219
220         Delete selected GCP
221           Deletes the currently selected GCP from the list.
222
223         Clear selected GCP
224           Resets all coordinates of the currently selected GCP to 0 (zero).
225
226         Reload GCPs from POINTS file
227           Reloads GCPs from the imagery group’s POINTS file.
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229         Recalculate RMS error
230           Recalculates  forward and backward RMS error for all GCP marked for
231           use (activated checkbox in first row).
232
233         Georectify
234           Uses i.rectify to georectify  all  images  in  the  source  imagery
235           group.
236
237   GCP Map Display Statusbar
238       The  GCP map display statusbar is similar to the statusbar in the regu‐
239       lar GRASS GIS map display with two differences, Go to has been replaced
240       with Go to GCP No. and Projection has been replaced with RMS error.
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242       If  Go  to  GCP  No. is selected, a GCP number can be given in the left
243       side of the statusbar and the source and target map canvas will be cen‐
244       tered  on the given GCP. Clicking on the map canvas will update coordi‐
245       nates for this GCP.
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247       If RMS error is selected, the overall forward and backward RMS error is
248       displayed.
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SEE ALSO

251        wxGUI
252       wxGUI components
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254        i.rectify, m.transform, v.rectify
255
256       See also video tutorials on GRASS Wiki.
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AUTHORS

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

264       Available at: wxGUI GCP Manager source code (history)
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266       Main  index  |  GUI  index  | Topics index | Keywords index | Graphical
267       index | Full index
268
269       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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273GRASS 7.8.2                                                       wxGUI.gcp(1)
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