Opened 21 years ago
Last modified 20 years ago
#213 closed defect (fixed)
shape-file polygons with multiple outer rings
Reported by: | Owned by: | warmerdam | |
---|---|---|---|
Priority: | high | Milestone: | |
Component: | default | Version: | unspecified |
Severity: | normal | Keywords: | |
Cc: | neteler@…, blazek@… |
Description
Hi Frank, Since this is my first bug submission please excuse any mistakes. I'm using OGR to read and display shape files as a part of a bigger project done in VC++. I have some problems which I tend to contribute to a possible insufficiency in the OGR shape file relating to reading of polygon shapes with interior rings. Namely, function SHPReadOGRObject in shape2ogr.cpp assumes that the first ring in a polygon is the outer one. Now, while reading the ESRI documentation on shape files I've come across a piece of info. which states that a polygon may contain multiple outer rings. The doc. also mentions that the order of vertices in a ring is different for outer and inner rings which kind of suggests one way of checking if a ring is an outer or an inner one. I just wanted your opinion on this and if you think that there would be another way of checking it. Finally, the bug manifest itself when for example countries that have islands (such as Russia) are to be displayed due to (in my opinion as least) the fact that the islands are read in by OGR as inner rings rather then as outer ones belonging to the same polygon. regards Ismar
Change History (4)
comment:2 by , 20 years ago
I have tried to fix that:http://mpa.itc.it/radim/shape2ogr.cpp-1.1.9-fix-1Radim
comment:3 by , 20 years ago
Frank, excuse me to bother you. Would it be possible to apply the patch of Radim to fix the reported problem? Thanks in advance, Markus
comment:4 by , 20 years ago
Radim, I have applied the patch with one tweak to produce MultiPolygons instead of GeometryCollections. However, I am still somewhat uncomfortable with the change and I hope to review it to see if there are any efficiency gains I can make. I am concerned about doing alot of extra computation work during reading of large complex polygons. Thanks for the contribution, and sorry for taking to long to apply it.
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