Plugins interpolation
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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 intiuitive graphical user interface for creating interpolated raster layers (See Figure <A HREF="#fig:interpolation_dialog">56</A>). The plugin requires the following parameters to be specified before running: <P>
- Input vector layer: Specify the input point vector layer from a list of loaded point layers.
- Interpolation attribute: Select attribute column to be used for interpolation or enable the 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.
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<A NAME="fig:interpolation_dialog"></A><A NAME="17"></A>
[clip=true, width=9cm]interpolate_dialog
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<P> Using the plugin<A NAME="interpolation_usage"></A> <P>
- Start QGIS and load an point vector layer (e.g., elevp.csv).
- Load the Interpolation plugin in the Plugin Manager (see Section #sec:load_core_plugin) and click on the interpolationInterpolation icon which appears in the QGIS toolbar menu. The Interpolation plugin dialog appears as shown in Figure 56.
- Select an input layer (e.g., elevp...) and column (e.g. ELEV) for interpolation.
- Select an interpolation method (e.g. Triangular interpolation...), and specify the number of rows and columns (e.g. 3663 cols and 1964 rows (this is equivalent to a 1000 meter pixel resolution)) as well as the raster output filename (e.g., elevation_tin).
- Click Ok.
- 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 in the Symbology tab. Or you can define a new color table as described in Section #label_rasterprop.
<P> In Figure 57 you see the IDW interpolation result with a 366 cols x 196 rows (10 km) resolution for the elevp.csv data visualized using the Pseudocolor color table. The processing only takes a few minutes, and covers the northern part of Alaska.
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<A NAME="fig:interpolation_idw"></A><A NAME="47"></A>
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[clip=true, width=12cm]interpolate_idw
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