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qgis_contours [2021/02/17 09:12] – created bushwalkingqgis_contours [2023/03/06 08:01] (current) bushwalking
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   * GDAL : Raster Extraction : Contour (same as Raster -> Extraction -> Contour...)   * GDAL : Raster Extraction : Contour (same as Raster -> Extraction -> Contour...)
  
-Below is an example of contours created without and with [[depressionless_dem|sink removal]]. The contours on the right have been derived from a DEM where the sinks (in yellow on the left) have been filled.+Below is an example of contours created without and with [[qgis_depressionless_dem|sink removal]]. The contours on the right have been derived from a DEM where the sinks (in yellow on the left) have been filled.
 {{:2019_02_08_12_17_09_untitled_project_qgis.png?300|}} {{:2019_02_08_12_17_09_untitled_project_qgis.png?300|}}
 {{:2019_02_08_12_17_57_untitled_project_qgis.png?300|}} {{:2019_02_08_12_17_57_untitled_project_qgis.png?300|}}
 +
 +It is worth noting that a [[qgis_depressionless_dem|depressionless DEM]] does not guarantee that there will be no contour sinks. A deep diagonal channel combined with a small contour interval can still cause sinks. {{::qgis_raw_contours.png?nolink&600|}}
 +
 +See [[https://gis.stackexchange.com/questions/390221/fix-unwanted-sink-contours-from-hydrologically-correct-dem/|GIS Stack Exchange]] for options of how to deal with this.
  
 ===== Simplifying ===== ===== Simplifying =====
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 {{:contour_loops.png|}} {{:contour_loops.png|}}
  
-Here is one approach, which involves adding a length attribute to each contour, and removing those that fall below a certain length. It may cause issues if you have short sections of contour near the edge of the map that you need.+Here is one approach, which involves adding a length attribute to each contour, and removing those that fall below a certain length. It may cause issues if you have short sections of contour near the edge of the map that you need. However, that shouldn't be a problem in most scenarios.
  
   * Open Attribute Table (F6)   * Open Attribute Table (F6)
qgis_contours.1613513573.txt.gz · Last modified: 2021/02/17 09:12 by bushwalking

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