Digitizing Detailed Geometry as Drainage Channel
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General
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You can add a polygon to a wastewater structure just with drawing a simple line. The function creates a rectangle from the line with a width of 20cm. This is specially useful for manholes with function drainage channel.

Digitizing tool
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* Select the **vw_tww_wastewater_structure** layer
* Use the **Identify features** tool on the object to which you want to add a drainage channel geometry
* In the Feature Attributes window:go to the **Action** menu and choose **Digitize Drainage Channel**

.. figure:: images/digitize_actionmenu.jpg

or

* Right click the object and select the **vw_tww_wastewater_structure** layer and the record
* Choose **Digitize Drainage Channel**

.. figure:: images/digitize_detail_geom_select1.jpg

* You can now start digitizing: draw a simple line with two clicks.
* The polygon with a width of 20 cm is created in the **vw_wastewater_structure** layer (layergroup Wastewater Structures)
* In order to alter the width, press Ctrl during digitizing. After the second click, alter the width in the popup window.