Plugins interpolation

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2009年10月6日 (火) 02:23時点におけるSanak (トーク | 投稿記録)による版

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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 54). The plugin requires the following parameters to be specified before running:

  • 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 CheckBox.pngUse Z-Coordinate checkbox to use the layers stored Z values.
  • Interpolation Method: Select interpolation method. This can be either Triangulated Irregular Network (TIN) ... SelectString.png or Inverse Distance Weighted (IDW) ... SelectString.png.
  • 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.
図 54: Interpolation Plugin Nix.png
Interpolate dialog.png
Using the plugin

  1. Start QGIS and load an point vector layer (e.g., elevp.csv).
  2. Load the Interpolation plugin in the Plugin Manager (see Section sec:load_core_plugin) and click on the Interpolation.png Interpolation icon which appears in the QGIS toolbar menu. The Interpolation plugin dialog appears as shown in Figure 54.
  3. Select an input layer (e.g., elevp ... SelectString.png) and column (e.g. ELEV) for interpolation.
  4. Select an interpolation method (e.g. Triangular interpolation ... SelectString.png), 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).
  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 ... SelectString.png as Color Map in the Symbology tab. Or you can define a new color table as described in Section label_rasterprop.

In Figure 55 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.

図 55: Interpolation of elevp data using IDW method Nix.png
Interpolate idw.png