[postgis-users] shp2pgsql and clockwise vertices?

[Hubert Fröhlich]

Hi list,

I use PostGIS 0.7.5 and PostgreSQL 7.3.4.

I produced a PostGIS table with MULTIPOLYGONS (150 rows) and wanted to 
export them to shape with pgsql2shp .

When filling the PostGIS table I t took care about:
- filling only with multipolygons containing 1 polygon with vertices in 
clockwise order.

However, when I produced the shapes and examined the data, I realized 
that  in some (few) shapes the orientation changed to counterclockwise.

Then I tested the same with a modified PostGIS table by deleting some 30 
rows. Result: again some shapes with changed orientation, but not the 
same shapes as in the first test with the 150 shapes.

What is the reason for this mixing up the shape orientation?

Any hints will be appreciated.
Thanks.

Hubert


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Dr.-Ing. Hubert Fröhlich			
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