Geografic-Information-System/gui/wxpython/vdigit/g.gui.vdigit.html

<!-- meta page description: wxGUI Vector Digitizer -->
<!-- meta page index: topic_gui|GUI -->
<h2>DESCRIPTION</h2>

The <b>vector digitizer</b> is a <em><a href="wxGUI.html">wxGUI</a></em>
component intended for interactive editing and digitizing vector maps
(see <em><a href="v.edit.html">v.edit</a></em> for non-interactive
vector editing GRASS capabilities).

<p>
Note that only vector maps stored or generated in the <i>current</i>
mapset can be opened for editing.

<p>
The digitizer allows editing of 2D vector features (points, lines,
centroids, boundaries, and areas).

<p>
Vector features can be selected by mouse (bounding box or simply by
mouse click, see select threshold
in <i>Settings&rarr;General&rarr;Select threshold</i>), or by query
(eg. by line length, see <i>Settings&rarr;Query Tool</i>).

<h3>STARTING THE DIGITIZER</h3>

The vector digitizer can be launched from Map Display toolbar by selecting
&quot;Digitize&quot; from <i>Tools</i> combobox. Vector map is
selectable for editing from Digitizer toolbar (&quot;Select vector
map&quot; combobox, note that only vector maps from the current layer
tree in Layer Manager are listed).

The vector digitizer can alternatively be activated from the contextual
menu in the Layer Manager by selecting "Start editing" on selected vector
map in the layer tree, or directly from the Layer Manager
toolbar <img src="icons/edit.png" alt="icon">.

The vector digitizer also can also be launched from the command line as a
stand-alone application <em>g.gui.vdigit</em>.

<h3>CREATING A NEW VECTOR MAP</h3>

A new vector map can be easily created from the digitizer toolbar by
selecting &quot;New vector map&quot; in &quot;Select vector map&quot;
combobox. A new vector map is created, added to the current layer tree
in Layer Manager and opened for editing. &quot;Select vector map&quot;
combobox in the digitizer toolbar also allows to easily switch between
vector maps to be edited.

<h3>EDITING AN EXISTING VECTOR MAP</h3>

An existing vector map selected in the digitizer toolbar in the
&quot;Select vector map&quot; combobox. This map is then opened for editing
and added to the current layer tree in the <em>Layer Manager</em>. This
&quot;Select vector map&quot; combobox in the digitizer toolbar also allows
to easily switch between vector maps to be edited.

<h3>USING A RASTER BACKGROUND MAP</h3>

In order to digitize from a raster map, simply load the map into the
<em>Map Display</em> using the <em>Layer Manager</em>. Then start digitizing,
see below for details.

<h3>USING A VECTOR BACKGROUND MAP</h3>

The vector digitizer allows you to select a &quot;background&quot; vector map.
Loading it within the digitizer is different from simply loading it via 
<em>Layer Manager</em> since direct interaction with single vector features
then becomes possible.<br>
A background map can be selected from the map layer contextual menu, in
<em>Layer Manager</em> (&quot;Use as Background Map&quot;). Newly digitized vector
features are snapped in the given threshold to the features from the
background map. Vector features may be also copied from the background
map by &quot;Copy features from (background) vector map&quot; tool
from the digitizer toolbar.

<h3>DIGITIZER TOOLBAR</h3>

<center>
<br>
<img src="vdigit_toolbar.jpg" border="1" alt="Vector Digitizer Toolbar">
<br><br>
</center>

<dl>
  <dt><img src="icons/point-create.png" alt="icon">&nbsp;
    <em>Digitize new point</em></dt>
  <dd>Add new point to vector map and optionally define its
    attributes.</dd>
  
  <dt><img src="icons/line-create.png" alt="icon">&nbsp;
    <em>Digitize new line</em></dt>
  <dd>Add new line to vector map and optionally define its
    attributes.</dd>

  <dt><img src="icons/boundary-create.png" alt="icon">&nbsp;
    <em>Digitize new boundary</em></dt>
  <dd>Add new boundary to vector map and optionally define its
    attributes.</dd>
  
  <dt><img src="icons/centroid-create.png" alt="icon">&nbsp;
    <em>Digitize new centroid</em></dt>
  <dd>Add new centroid to vector map and optionally define its
    attributes.</dd>

  <dt><img src="icons/polygon-create.png" alt="icon">&nbsp;
    <em>Digitize new area</em></dt>
  <dd>Add new area (closed boundary and one centroid inside) to vector
    map and optionally define its attributes.</dd>
  
  <dt><img src="icons/vertex-move.png" alt="icon">&nbsp;
    <em>Move vertex</em></dt>
  <dd>Move selected vertex of linear feature. Thus shape of linear
    feature is changed.</dd>

  <dt><img src="icons/vertex-create.png" alt="icon">&nbsp;
    <em>Add vertex</em></dt>
  <dd>Add new vertex to selected linear feature (shape not
    changed).</dd>

  <dt><img src="icons/vertex-delete.png" alt="icon">&nbsp;
    <em>Remove vertex</em></dt>
  <dd>Remove selected vertex from linear feature. Thus shape of selected
  feature can be changed.</dd>
  
  <dt><img src="icons/line-edit.png" alt="icon">&nbsp;
    <em>Edit line/boundary</em></dt>
  <dd>Edit selected linear feature, add new segments or remove
  existing segments of linear feature.</dd>

  <dt><img src="icons/line-move.png" alt="icon">&nbsp;
    <em>Move feature(s)</em></dt>
  <dd>Move selected vector features. Selection can be done by mouse or
    by query.</dd>

  <dt><img src="icons/line-delete.png" alt="icon">&nbsp;
    <em>Delete feature(s)</em></dt>
  <dd>Delete selected vector features (point, line, centroid, or
  boundary). Selection can be done by mouse or by query.</dd>

  <dt><img src="icons/polygon-delete.png" alt="icon">&nbsp;
    <em>Delete areas(s)</em></dt>
  <dd>Delete selected vector areas. Selection can be done by mouse
  or by query.</dd>

  <dt><img src="icons/cats-display.png" alt="icon">&nbsp;
    <em>Display/update categories</em></dt>
  <dd>Display categories of selected vector feature. Category settings
  can be modified, new layer/category pairs added or already defined pairs
  removed.</dd>

  <dt><img src="icons/attributes-display.png" alt="icon">&nbsp;
    <em>Display/update attributes</em></dt>
  <dd>Display attributes of selected vector feature (based on its
    category settings).  Attributes can be also modified. Same
    functionality is accessible from Main toolbar "Query vector map
    (editable mode)".</dd>

  <dt><img src="icons/tools.png" alt="icon">&nbsp;
    <em>Additional tools</em></dt>
  <dd>
    <ul>
      <li><em>Break selected lines/boundaries at intersection</em><br> Split
	given vector line or boundary into two lines on given position
	(based on <em><a href="v.clean.html">v.clean</a></em>,
	<tt>tool=break</tt>).</li>

      <li><em>Connect two selected lines/boundaries</em><br> Connect selected
	lines or boundaries, the first given line is connected to the
	second one. The second line is broken if necessary on each intersection.
	The lines are connected only if distance between them is not greater
	than snapping threshold value.</li>

      <li><em>Copy categories</em><br>Copy category settings of
	selected vector feature to other vector
	features. Layer/category pairs of source vector features are
	appended to the target feature category settings. Existing
	layer/category pairs are not removed from category settings of
	the target features.</li>

      <li><em>Copy features from (background) map</em><br> Make identical copy of
	selected vector features. If a background vector map has been 
	selected from the Layer Manager, copy features from background 
	vector map, not from the currently modified vector map.</li>

      <li><em>Copy attributes</em><br>Duplicate attributes settings of
	selected vector feature to other vector features. New
	category(ies) is appended to the target feature category
	settings and attributes duplicated based on category settings
	of source vector features. Existing layer/category pairs are
	not removed from category settings of the target
	features.</li>

      <li><em>Feature type conversion</em><br> Change feature type of selected
	geometry features. Points are converted to centroids,
	centroids to points, lines to boundaries and boundaries to
	lines.</li>

      <li><em>Flip selected lines/boundaries</em><br> Flip direction of
	selected linear features (lines or boundaries).</li>

      <li><em>Merge selected lines/boundaries</em><br> Merge (at least two)
	selected vector lines or boundaries. The geometry of the
	merged vector lines can be changed. If the second line from
	two selected lines is in opposite direction to the first, it
	will be flipped. See also
	module <em><a href="v.build.polylines.html">v.build.polylines</a></em>.</li>

      <li><em>Snap selected lines/boundaries (only to nodes)</em><br> Snap
	vector features in given threshold. See also
	module <em><a href="v.clean.html">v.clean</a></em>. Note that
	this tool supports only snapping to nodes. Snapping to vector
	features from background vector map is not currently
	supported.</li>

      <li><em>Split line/boundary</em><br>Split selected line or boundary on
      given position.</li>

      <li><em>Query tool</em><br>Select vector features by defining a threshold for
        min/max length value (linear features or dangles).</li>

      <li><em>Z-bulk labeling of 3D lines</em><br> Assign z coordinate values to 3D
	vector lines in bounding box. This is useful for labeling contour lines.</li>
    </ul>
  </dd>

  <dt><img src="icons/undo.png" alt="icon">&nbsp;
    <em>Undo</em></dt>
  <dd>Undo previous operations.</dd>

  <dt><img src="icons/redo.png" alt="icon">&nbsp;
    <em>Redo</em></dt>
  <dd>Redo previous operations.</dd>

  <dt><img src="icons/settings.png" alt="icon">&nbsp;
    <em>Settings</em></dt>
  <dd>Digitizer settings.</dd>

  <dt><img src="icons/quit.png" alt="icon">&nbsp;
    <em>Quit digitizing tool</em></dt>
  <dd>Changes in vector map can be optionally discarded when
  digitizing session is quited.</dd>

</dl>

<h2>NOTES</h2>

<dl><dt><b>Mouse button functions:</b><dd>
	<dt><i>Left</i>   - select or deselect features</dt>
	<dt><i>Control+Left</i> - cancel action or undo vertex when digitizing lines</dt>
	<dt><i>Right</i>  - confirm action</dt>
</dl>

<p>
<i>Dead (deleted)</i> features are only marked as 'dead' in the geometry file
but remain there and occupy space. Any vector module
used afterwards on this vector map which really reads and writes
vector geometry (so not <em><a href="g.copy.html">g.copy</a></em>)
will write only features which are 'alive'.

<p>
<i>Added or modified</i> vector features are <i>snapped</i> to
existing vector features (Settings&rarr;General&rarr;Snapping). To
disable snapping set the snapping threshold to '0'.

<p>
If the digitizer crashes for some reason, the changes are
automatically saved. Broken topology can be repaired by running
<em><a href="v.build.html">v.build</a></em>.

<p>
GRASS GIS uses a topological vector format, meaning that a common boundary of 
two polygons is only stored once. When digitizing polygons it is thus important
to be able to only draw each boundary once. When drawing a polygon adjacent to an
existing polygon, one has to first split the existing boundary at the points where 
the new boundary will be attached. Snapping should be set to ensure that the new 
boundaries are automatically attached to the chosen points.

<h2>REFERENCES</h2>

<ul>
  <li><a href="http://grass.osgeo.org/programming7/veditlib.html">GRASS Vedit Library</a></li>
  <li><a href="http://grasswiki.osgeo.org/wiki/Vector_Database_Management">Vector Database Management</a> (Wiki page)</li>
</ul>

<h2>SEE ALSO</h2>

<em>
<a href="wxGUI.html">wxGUI</a><br>
<a href="wxGUI.components.html">wxGUI components</a>
</em>

<p>
<em>
<a href="v.edit.html">v.edit</a>,
<a href="v.category.html">v.category</a>,
<a href="v.build.html">v.build</a>
</em>

<p>
See also the <a href="http://grasswiki.osgeo.org/wiki/WxGUI_Vector_Digitizer">WxGUI Vector Digitizer Wiki page</a>
including <a href="http://grasswiki.osgeo.org/wiki/WxGUI_Vector_Digitizer#Vector_tutorials">video
tutorials</a>.

<h2>AUTHOR</h2>

Martin Landa, FBK-irst (2007-2008), Trento, Italy, and Czech Technical
University in Prague, Czech Republic

<p>
<i>$Date$</i>