[QGIS-trac] Re: [Quantum GIS] #3187: transform ring into new polygon

[Quantum GIS]

#3187: transform ring into new polygon
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   Reporter:  mlennert          |              Owner:  nobody       
       Type:  enhancement       |             Status:  new          
   Priority:  minor: annoyance  |          Milestone:  Version 1.6.0
  Component:  Build/Install     |            Version:               
   Keywords:                    |   Platform_version:               
   Platform:  All               |           Must_fix:  No           
Status_info:  0                 |  
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Comment(by mlennert):

 Replying to [comment:1 lutra]:
 > try import the polygon (with the ring) into a GRASS mapset, you'll have
 automatically your rings placed into a polygon layer, then with "save
 as..." you can get out the mapset as shapfiles... is this enough?

 This is the solution I currently give to people who are confronted with
 the issue, although it is not as automatic as you say: GRASS only
 recognizes a surface surrounded by boundary lines as area if it contains a
 centroid. A simple import with v.in.ogr does not insert such centroids
 automagically, you have to do that by hand with v.digit (or the QGIS GRASS
 digitizer) befor re-exporting the layer to shapefile.

 So, no, I don't think this is really enough. It shouldn't be too difficult
 to add one (or more) of the several options

 - "fill ring with a polygon"
 - copy boundary lines for reuse in a new polygon. Currently, IIUC, when
 editing a polygon layer, you can only select and copy polygons, not
 boundaries.
 - draw a polygon within an already existing larger polygon and to say that
 an island should be created in the larger polygon along the boundaries of
 the new one.

 Just these little things that make life a bit easier...
 ;-)

 Moritz

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Ticket URL: <http://trac.osgeo.org/qgis/ticket/3187#comment:2>
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