[gdal-dev] Closed polyline from DXF as line or area?

[Zoltan Szecsei]

Hiya,

My first thought is that the documentation must change.
If I had perimeter fence features on some agricultural fields, I would 
want the field feature to be a polygon but not the (closed) fence feature.

Surely the flexible way to go is exactly what is currently happening.
If a DXF user wants to create polygons from closed lines then surely 
that should be a post-process. ie: select lines with layer=x, 
linestyle=y etc etc, and convert these to polygons?

My 2c

Regards,
Zoltan


On 2015/01/26 16:18, Jukka Rahkonen wrote:
> Spotted from gis.stackexchange:
>
> http://gis.stackexchange.com/questions/131765/ogr-dxf-closed-polyline-conversion
>
> The DXF driver documentation claims that closed polylines from DXF are
> converted into polygons but that does not seem to happen. By comparing the
> DXF snipped from stackexchange
>
> ENTITIES
>    0
> LWPOLYLINE
>    5
> 20000
>    8
> 0
> 100
> AcDbEntity
> 100
> AcDbPolyline
>   70
> 1
>   90
> 4
>
> with a DXF specification
> http://www.autodesk.com/techpubs/autocad/acad2000/dxf/lwpolyline_dxf_06.htm
> I can read that LWPOLYLINE [code 70] is defined with flag 1 [closed]. But
> could someone interpret what does it mean in GIS context? Should a closed
> CAD polyline be translated into LINEARRING or POLYGON in WKT?
>
> -Jukka Rahkonen-
>
>
>
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Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

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