====== Parallel Extraction ======
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This page describes how to use the extension "Parallel Extraction".\\
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**Feature Extraction Standard - Pro, Publisher Client**\\
{{orbitgis:how_to_find.png?25&nolink|}} [[195:desktop:workspace:main_toolbar|Main Toolbar]] > Extensions >  Parallel Extraction\\
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The "Parallel Extraction" tab makes it possible to extract in a semi-automatic way linear features .\\


{{:170:desktop_ext:parallel_extraction_tab_16.png?nolink&900|}}


===== Concepts =====
**Parallel extraction**\\
Extraction of several parallel line features in the same time.

**Files & folders**\\
A line vector dataset must be available in the [[195:desktop:dataset:index|Dataset List]]. For the extension to be enabled, one vector dataset must be set as Recordable. All extracted objects will be automatically saved in the [[195:desktop:dataset:operations_indicators|Recordable Dataset]].
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===== Parallel Extraction Tab =====

=== Set===
**New Set** \\
Create a new set of points in order to extract features.
Define your extraction with 3 clicks:
  * First click defines the starting position of the extraction
  * Second click defines the direction
  * Third click, perpendicular on the direction defines the width of the profile

**Stop Set** \\
Stop the process during the definition.

**Clear Set** \\
Delete all points and extracted lines.

=== Slice ===

**Thickness** \\
Adjust the slice thickness by using the slider. The default is set in [[195:desktop:preferences:parallel_extraction|]]

**Show on map** \\
Check to display the slices on map or not.

===Extraction Toolbar===

In order, from left to right, the icons correspond to:
  * advance extracted line with one small step
  * advance extracted line with one normal step
  * advance extracted line with one large step
The defaults for the steps are set in Preferences of Parallel Extraction.
  * snap - automatically try to snap the points to the pointcloud
  * save point - press to register the last drawn vertex if no modification are necessary ( grayed out if point position is modified)
  * delete the extracted segment that corresponds to the last step
  * move the view to the beginning
  * move the view one step back
  * move the view one step forward
  * stop all - stop the extraction and automatically copy the extracted lines to the Recordable dataset.

=== Context Menu ===

By clicking right on any of the points, a series of options become available :

  * Stop Line - stops the extraction and copies the line to the recordable dataset
  * Interrupt line - stops momentarily the extraction
  * Restart Line - restarts an interrupted extraction 
  * Remove Point - deletes the point
  * Focus Views - focus the map and the tab on the selected point
  * Ungroup - removes the grouping of two points
  * Set direction - the direction of the extraction will be based on the selected point 

=====Workflow=====

  - Open the run that contains the portion to extract
  - A line vector file must be set as the recordable dataset.
  - Switch to Map 3D mode.
  - Open the Parallel Extraction extension
  - Press "New Set" and click on the Map Canvas defining the starting point, direction and width of the profile.This will automatically display the profile in the tab
  - Define the extraction points location , by clicking on the profile. Each point will be the base for an extracted line. By pressing "Ctrl" two points can be grouped. A group is a set of points that behave as a single entity.For example group together the points that represent the upper and lower part of a curbstone.Like this both will be extracted as separate vectors and their position can be adjusted with only one click.
  - Define as many points as needed. For example define a group for each side of the road containing the two extremities of the curbstone, and one point the the middle guardrail. Each of them will result in the extraction of a polyline.
  - Start extraction by moving forward with small, normal or large steps
  - For each step adjust points or groups position by moving them.To move a point, hover over it with the mouse until the cursor appearance changes, then drag the point to it's correct location.
  - Use the Snap function to let the software to find automatically the right position for the points 
  - Navigate through the extracted portion using the tools in the Extraction Toolbar
  - Finnish or stop the extraction using Stop All or the context menu