オンザフライプロジェクションの指定
Define On The Fly (OTF) Projection
QGIS does not have OTF projection enabled by default, and this function is currently only supported for vector layers. To use OTF projection, you must open the mActionOptionsProject Properties dialog, select a CRS and activate the Enable on the fly projection checkbox. There are two ways to open the dialog: <P>
- Select mActionOptionsProject Properties from the Edit (Gnome, OSX) or Settings (KDE, Windows) menu.
- Click on the mIconProjectionDisabledprojector icon in the lower right-hand corner of the statusbar.
<P> If you have already loaded a layer, and want to enable OTF projection, the best practice is to open the Coordinate Reference System tab of the Project Properties dialog, select the CRS of the currently loaded layer, and activate the Enable on the fly projection checkbox. The mIconProjectionEnabledprojector icon will show a green hook and all subsequently loaded vector layers will be OTF projected to the defined CRS.
<P> The Coordinate Reference System tab of the Project Properties dialog contains four important components as shown in Figure <A HREF="#fig:projections">25</A> and described below.
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[clip=true, width=12cm]projectionDialog
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- Enable on the fly projection<A NAME="70"></A> - this checkbox is used to enable or disable OTF projection. When off, each layer is drawn using the coordinates as read from the data source. When on, the coordinates in each layer are projected to the coordinate reference system defined for the map canvas.
- Coordinate Reference System - this is a list of all CRS supported by QGIS, including Geographic, Projected and Custom coordinate reference systems. To use a CRS, select it from the list by expanding the appropriate node and selecting the CRS. The active CRS is preselected.
- Proj4 text - this is the CRS string used by the Proj4 projection engine. This text is read-only and provided for informational purposes.
- Search - if you know the EPSG identifier or the name for a Coordinate Reference System, you can use the search feature to find it. Enter the identifier and click on Find.
- Recently used CRS - if you have certain CRS that you frequently use in your everyday GIS work, these will be displayed as 'quick access' buttons at the bottom of the Projection Dialog. Click on one of these buttons to select the associated CRS.
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