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| − | <H3>
| + | --[[利用者:Sanak|Sanak]] 2009年10月4日 (日) 09:54 (UTC)このページは削除予定です。 |
| − | Setting the Snapping Tolerance and Search Radius
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| − | </H3>
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| − | <P>
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| − | Before we can edit vertices, it is very important to set the snapping
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| − | tolerance and search radius to a value that allows us an optimal editing of
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| − | the vector layer geometries.
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| − | <P>
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| − | Snapping tolerance
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| − | <P>
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| − | Snapping tolerance is the distance QGIS uses to search for the
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| − | closest vertex and/or segment you are trying to
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| − | connect when you set a new vertex or move an existing vertex. If you aren't
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| − | within the snap tolerance, QGIS will leave the vertex where you release the
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| − | mouse button, instead of snapping it to an existing vertex and/or segment.
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| − | <P>
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| − | <OL>
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| − | <LI>A general, project wide snapping tolerance can be defined choosing
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| − | Settings > mActionOptionsOptions.
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| − | (On Mac: go to QGIS > Preferences, on Linux: Edit > mActionOptionsOptions.)
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| − | In the Digitizing tab you can select between to vertex, to segment or
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| − | to vertex and segment as default snap mode. You can also define a default
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| − | snapping tolerance and a search radius for vertex edits. The tolerance an be set either in map units or in pixels.
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| − | In our digitizing project (working with the
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| − | Alaska dataset), the units are in feet. Your results may vary, but something
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| − | on the order of 300ft should be fine at a scale of 1:10 000 should be a
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| − | reasonable setting.
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| − | </LI>
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| − | <LI>A layer based snapping tolerance can be defined by choosing
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| − | Settings (or File) > mActionOptionsProject
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| − | Properties.... In the General tab, section Digitize you
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| − | can click on Snapping options... to enable and adjust snapping
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| − | mode and tolerance on a layer basis (see Figure <A HREF="#fig:snappingoptions">15</A>).
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| − | </LI>
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| − | </OL>
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| − | <P>
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| − | <DIV ALIGN="CENTER"><A NAME="fig:snappingoptions"></A><A NAME="580"></A>
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| − | <TABLE>
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| − | <CAPTION ALIGN="BOTTOM"><STRONG>Figure:</STRONG>
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| − | Edit snapping options on a layer basis </CAPTION>
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| − | <TR><TD>
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| − | <DIV ALIGN="CENTER">
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| − | </DIV>
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| − | <P></P>
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| − | <DIV ALIGN="CENTER"> [clip=true, width=14cm]editProjectSnapping
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| − | </DIV></TD></TR>
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| − | </TABLE>
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| − | </DIV>
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| − | <P>
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| − | Search radius
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| − | <P>
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| − | Search radius is the distance QGIS uses to search for the closest
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| − | vertex you are trying to move when you click on the
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| − | map. If you aren't within the search radius, QGIS won't find and select
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| − | any vertex for editing and it will pop up an annoying warning to that effect.
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| − | Snap tolerance and search radius are set in map units or pixels, so you may find you
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| − | need to experiment to get them set right. If you specify too big of a
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| − | tolerance, QGIS may snap to the wrong vertex, especially if you are dealing
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| − | with a large number of vertices in close proximity. Set search radius too
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| − | small and it won't find anything to move.
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| − | | + | |
| − | <P>
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| − | The search radius for vertex edits in layer units can be defined in the
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| − | Digitizing tab under Settings >
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| − | mActionOptionsOptions. The same place where you define the
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| − | general, project wide snapping tolerance.
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