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Interpolation Plugin

The Interplation plugin can be used to generate a TIN or IDW interpolation of a point vector layer. It is very simple to handle and provides an intuitive graphical user interface for creating interpolated raster layers (See Figure_interpolation_1). The plugin requires the following parameters to be specified before running:

  • Input vector layer: Specify the input point vector layer(s) from a list of loaded point layers. If several layers are specified, then data from all layers is used for interpolation. Note: It is possible to insert lines or polygons as constraints for the triangulation, by specifying either “points”, “structure lines” or “break lines” in the Type selectstring combobox.
  • Interpolation attribute: Select attribute column to be used for interpolation or enable the checkbox Use Z-Coordinate checkbox to use the layers stored Z values.
  • Interpolation Method: Select interpolation method. This can be either ‘Triangulated Irregular Network (TIN)’ or ‘Inverse Distance Weighted (IDW)’.
  • Number of columns/rows: Specify the number row and colums for the output raster file.
  • Output file: Specify a name for the output raster file.

Figure Interpolation 1:

../../../_images/interpolate_dialog.png

Interpolation Plugin nix

Using the plugin

  1. Start QGIS and load a point vector layer (e.g., elevp.csv).
  2. Load the Interpolation plugin in the Plugin Manager (see Section Loading a QGIS Core Plugin) and click on the raster-interpolate Interpolation icon which appears in the QGIS toolbar menu. The Interpolation plugin dialog appears as shown in Figure_interpolation_1.
  3. Select an input layer (e.g., elevp selectstring) and column (e.g., ELEV) for interpolation.
  4. Select an interpolation method (e.g. ‘Triangulated Irregular Network (TIN)’), and specify a cellsize of 5000 as well as the raster output filename (e.g., elevation_tin).
  5. Click [OK].
  6. For the current example, double click elevation_tin in the layer list to open the raster Layer Properties dialog and select ‘Pseudocolor’ as Color Map selectstring in the Symbology tab. Or you can define a new color table as described in section Working with Raster Data.