[OSM-talk] Cannot correct ring self intersection

[Jukka Rahkonen]

Hi,

I found about 100 topology errors from polygons in Finland with the following
work flow:

- OSM-data are in PostGIS 
- I took polygons with topology errors directly into OpenJUMP map with db query:
  select * from osm_polygon where not  isvalid(way);
- I used OpenJUMP topology check tool which creates a new point layer
  showing the exact places of the errors
- That layer I converted to gpx and loaded into JOSM. Then I downloaded OSM data
    
  around error locations and made corrections.

Usually this works rather well.  But then I faced such a ring self-intersection
that I cannot correct it.  It is about a lake that intersects itself but also
shares one node with a road.  The place is here:  

http://www.openstreetmap.org/index.html?mlat=61.277669238738454&mlon=28.855010608222813&zoom=13

I was thinking that I should cut the lake polygon, draw a couple of new nodes
and connect the lake together again, but I just cannot split the lake boundary.
 How should I do it?

-Jukka Rahkonen-