Mark Adams wrote:
Emil,
Thanks, you are right, that works. I'd had the same response from Frank W.
I'm not sure where the format for these strings is specified or documented -
the only information I was able to find said to do things differently.
For the benefit of anyone else trying to use this functionality, I also
discovered that you could create a multi-polygon as follows:
POLYGON (( 501453.34 4800585.97, 501576.14 4800590.44, 501569.85 4800522,
501471.61 4800521.63, 501453.34 4800585.97 ))
Mark,
The format is OpenGIS Well Known Text geometry format from the Simple
Features for SQL Specification (99-049 I think). It is the same format
reported by ogrinfo, and the textual format of PostGIS or MySQL Spatial.
Technically the above is not a multi-polygon. A multi-polygon (in simple
features) is a collection of polygon objects. A polygon is one or more
rings, with one being the outer ring and the rest being inner rings. So
in the parliance I was used to in the old days, a polygon is an island
potentially with lakes cut out of it. A multipolygon is a much of such
islands.
Multipolygons use the MULTIPOLYGON keyword.
A 'polygon' object in a shapefile may be either a simple features POLYGON
or MULTIPOLYGON depending on whether there are multiple outer rings.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
