[QGIS-trac] [Quantum GIS] #2089: Buffer produces incorrect results

[Quantum GIS]

#2089: Buffer produces incorrect results
---------------------------------------------------------+------------------
   Reporter:  jaanvajakas                                |              Owner:  borysiasty
       Type:  bug                                        |             Status:  new       
   Priority:  critical: causes crash or data corruption  |          Milestone:            
  Component:  Python plugins and bindings                |            Version:  1.3.0     
   Keywords:                                             |   Platform_version:            
   Platform:  Windows                                    |           Must_fix:  No        
Status_info:  0                                          |  
---------------------------------------------------------+------------------
 To reproduce:
  1. create a new project in QGIS,
  2. add layer kirdem2.epg4326.shp using Layers -> Add vector layer...,
  3. Tools -> Geoprocessing tools -> Buffer(s), set buffer distance to
 -0.0003, choose output file, click OK

 Expected result: an inner buffer of the polygons in platte carree distance
 (not real distance, as interpreting degrees as meters would be ambiguous)

 Actual result: certainly not a buffer neither in platte carree distance
 nor in real geodetic distance nor any other projection. In some places,
 the buffer exceeds the original polygon border (see qgis_buffer_bug1.png);
 in some places, the buffer has "pixel artifacts" (qgis_buffer_bug1.png);
 some islands are missing altogether (qgis_buffer_bug2.png).

 The input data kirdem2.epg4326.shp is part of the publicly available
 dataset '01.09.2009a. asustusüksus SHP' (zip - 13,65 MB, 6.11.2009 ) on
 http://www.maaamet.ee/index.php?lang_id=1&page_id=272&menu_id=0
 (I cut a small part out and converted to EPSG:4326 using QGIS).

-- 
Ticket URL: <https://trac.osgeo.org/qgis/ticket/2089>
Quantum GIS <http://qgis.org>
Quantum GIS is an Open Source GIS viewer/editor supporting OGR, PostGIS, and GRASS formats