nettopologysuitepostgis
Can someone provide a precise definition of what a "non-noded intersection" is? There are various GIS platforms and toolkits that have errors with this text, and Google search results for this tend to fall in the category of "drop some precision and all your problems go away" without any real explanation of what's going wrong. Given two valid geometries, why would this error occur?
References to documentation would be most helpful.
In my experience this problem is nearly always caused by:
The "nudge" approach of the ST_Buffer solutions lets you get away with #2, but anything you can do to resolve these underlying causes, like snapping your geometry to a 1e-6 grid, will make your life easier. The buffered geometries are usually fine for intermediate calculations like overlap area, but you'll want to be careful about retaining them because they can make your close-but-not-quite problems worse in the long haul.
PostgreSQL's exception-handling capability lets you write wrapper functions to handle these special cases, buffering only when needed. Here's an example for ST_Intersection; I use a similar function for ST_Difference. You'll need to decide if the buffering and potential return of an empty polygon are acceptable in your situation.
CREATE OR REPLACE FUNCTION safe_isect(geom_a geometry, geom_b geometry)
RETURNS geometry AS
$$
BEGIN
RETURN ST_Intersection(geom_a, geom_b);
EXCEPTION
WHEN OTHERS THEN
BEGIN
RETURN ST_Intersection(ST_Buffer(geom_a, 0.0000001), ST_Buffer(geom_b, 0.0000001));
EXCEPTION
WHEN OTHERS THEN
RETURN ST_GeomFromText('POLYGON EMPTY');
END;
END
$$
LANGUAGE 'plpgsql' STABLE STRICT;
Another benefit with this approach is you can pinpoint the geometries that are actually causing your problems; just add some RAISE NOTICE statements in the EXCEPTION block to output WKT or something else that will help you track down the problem.
Your error says:
found non-noded intersection between LINESTRING(51020.5489171519 215, 51025.9092732259 215) and LINESTRING(51025.9092732259 215, 51011.7280780429 215) [ (51020.5489171519, 215, 53973.4510575744) ]
Had trouble visualizing it so I loaded your WKT to the Geometry Visualizer and found this on the upper right corner:
That's what's making your geometry invalid. You'll have to fix that corner if you want the error to go away. I think it's best to check your polygons for validity before you put them through any operations. Would save you a lot of headaches.
Best Answer
It means that nodes cannot be in the same spatial space during intersection. I drew you a picture.
These are the same lines, but intersected.
If you noticed, if I had dropped the node in the middle (since it is not needed) that the bottom diagram would be impossible.