[gdal-dev] S57 questions

Frank Warmerdam warmerdam at pobox.com
Mon May 31 23:14:41 EDT 2010

ogr user wrote:
> This patch does not do anything regarding direction of winding.
> What it does is - discover the exterior ring for a polygon, and make it
> the first ring in the polygon object. This was in response to your
> earlier comment that said "The S-57 driver uses
> OGRBuildPolygonFromEdges() to form the set of lines into a polygon.  No
> effort is currently made to properly represent exterior vs. interior
> rings as is required by the simple features geometry specification."
> This is that effort. FWIW, with this patch, polygons read from ENC data
> that were assembled "out of order" (i.e. exterior ring was assembled
> later than a first one) would be rearranged (in that exterior ring is
> found and made the "exterior" ring) so that they could be drawn/handled
> correctly using OGR geometry.


This would indeed be a useful change. I'd encourage you to file it in Trac
and I'll look at incorporating it.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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