Difference between revisions of "QGIS Extract Ground Elevation"

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=Method=
 
=Method=
 
<ol>
 
<ol>
<li>Ensure that the plugin has been loaded and that the line file is open.</li>
+
<li>Load DEM and 2d_zsh line layer files.</li>
<li>From the menu select ''Plugins >> mmqgis >> Modify >> Convert Geometry Type''.</li>
+
<li>Convert line vertexes to points, using the preferred method described in  ''Plugins >> mmqgis >> Modify >> Convert Geometry Type''.</li>
 
[[File:QGIS Lines to Points.jpg|500px]]
 
[[File:QGIS Lines to Points.jpg|500px]]
 
<li>Set the following:<br>
 
<li>Set the following:<br>

Revision as of 16:52, 19 February 2018

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 the points snapped to breaklines
  • Define ground elevation for 1D nodes/pits snapped to 1D channel/pipes
  • etc...

In the example below, the ground elevation for the 2d_zsh point layer in the TUFLOW Tutorial 03 is extracted from the DEM file.

Method

  1. Load DEM and 2d_zsh line layer files.
  2. Convert line vertexes to points, using the preferred method described in Plugins >> mmqgis >> Modify >> Convert Geometry Type.
  3. QGIS Lines to Points.jpg
  4. Set the following:
    • The source layer to be the line file you wish to convert
    • The new geometry type to Nodes
    • The output file
    The plugin will create a new point file which contains all vertices along the line. If you wish to create intermediate points along the line you will need to use an alternate plugin. A plugin called Profile from Line appears to do this.