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QGIS Extract Ground Elevation: Difference between revisions

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=Introduction=
This page describes the method for extracting ground elevation (or any other variable) from raster files or polygon attribute using "Point Sampling Tool". This method is useful when you want to:
* Extract ground elevation for theat points snapped to breaklines
* Define ground elevation forat 1D nodes/pits snapped to 1D channel/pipes
* etc...
In the example below, the "Z" attribute (ground elevation) forof the 2d_zsh point layer in the [[Tutorial_Module03Tutorial_M11 | TUFLOW Tutorial 0311]] is extracted from the DEM file.
 
=Method=
<ol>
<li>LoadEnsure that DEM and 2d_zsh line layer files. are opened, and the Point Sampling Tool plugin has been installed (Plugins >> Manage and Install Plugins >> Point Sampling Tool) </li>
<li>Convert line vertexesvertices to points, using the preferred method described in the [[QGIS_Convert_Lines_to_Points ''Plugins| >>QGIS mmqgisConvert >>Lines Modify >> Convertto GeometryPoints]] Type''.page</li>
<li>Open the Point Sampling Tool</li>
[[File:QGIS Lines to Points.jpg|500px]]
[[File:QGIS Extract Ground Elevation 001.png|700px]]
<li>Set the following:<br>
* TheSelect sourcethe point layer toconverted beat thestep line2 fileas the you"Layer wishcontaining tosampling convertpoints"
* Select all the attribute in the point layer as well as the DEM as the "Layers to get value from"
* The new geometry type to '''Nodes'''
* TheSet the output layer file name
The plugin will create a new point layer file which contains all verticesattributes alongin thea line.2d_zsh layer Ifand youthe wishbed toelevation create intermediate points alongas the line5th you will need to use an alternate pluginattribute. A plugin called ''Profile from Line'' appears to do this.
<li>Open the Attribute Table of the newly created layar. Toggle editing and update "Z" attribute with "dem_m01" as shown in the image below</li>
[[File:QGIS Extract Ground Elevation 002.png|600px]]<br>
This point layer is now ready to be input with the 2d_zsh line layer into the TUFLOW model.
</ol>
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