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データ補間プラグイン

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 layers: 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 combo box.

  • 補間する属性: 補間に使用する属性カラムを選択するか,格納されたZ値を使用するには checkbox Z座標を使用する チェックを有効にします.

  • Interpolation Method: Select the interpolation method. This can be either ‘Triangulated Irregular Network (TIN)’ or ‘Inverse Distance Weighted (IDW)’. With the TIN method you can create a surface formed by triangles of nearest neighbour points. To do this, circumcircles around selected sample points are created and their intersections are connected to a network of non overlapping and as compact as possible triangles. The resulting surfaces are not smooth. When using the IDW method the sample points are weighted during interpolation such that the influence of one point relative to another declines with distance from the unknown point you want to create. The IDW interpolation method also has some disadvantages: the quality of the interpolation result can decrease, if the distribution of sample data points is uneven. Furthermore, maximum and minimum values in the interpolated surface can only occur at sample data points. This often results in small peaks and pits around the sample data points.

  • カラム/行の数: 出力するラスタファイルの 行またはカラムの数を指定します。

  • 出力ファイル: 出力するラスタファイルの名称を指定します。

  • checkbox 結果をプロジェクトに追加する マップキャンバスに結果をロードします。

Note that using lines as constraints for the interpolation the triangulation (TIN method) you can either use ‘structure lines’ or ‘break lines’. When using ‘break lines’ you produce sharp breaks in the surface while using ‘structure lines’ you produce continous breaks. The triangulation is modified by both methods such that no edge crosses a breakline or structure line.

Figure Interpolation 1:

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

Interpolation Plugin nix

プラグインの利用

  1. Start QGIS and load a point vector layer (e.g., elevp.csv).
  2. Load the Interpolation plugin in the Plugin Manager (see プラグインダイアログ) and click on the Raster ‣ Interpolation ‣ raster-interpolate Interpolation , which appears in the QGIS menu bar. 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. 補間法(e.g. 三角形分割補間（TIN）)を選択し、出力ラスタのファイル名（e.g., elevation_tin）および5000のセルサイズを特定します。

  5. [OK] をクリックします。