Hi,
It has been a long time I've not played with noding package, but would a
Noder (ex. MCIndexNoder) with an appropriate SegmentIntersector be a
solution ?
Michaël
Unfortunately the DE-9IM model (which is used to define the OGC SFS
spatial predicates which JTS implements) doesn't allow specifying true
line crossing (as far as I can tell). So there's no direct way to
compute this using existing JTS predicates.
Determining this condition would require building a simple topological
structure for each LineString (essentially a chain of segments). Then
each segment can be checked against all others to determine if a true
crossing exists. There are three situations which need to be checked:
a) crossing at interior point of 2 segments, (b) crossing at a vertex
on one segment, and (c) crossing at vertices on both segments. (This
is why the full topology is required, rather than just checking
segments individually). To make this performant, the segments would
need to be indexed in some way (for instance, using the JTS STRtree
This seems like a useful predicate to have for JTS. Feel free to post
the code if you implement it.
On Mon, Oct 20, 2014 at 6:28 AM, Tore Halset <[email protected]
<mailto:[email protected]>> wrote:
Hello.
I have two LineString depth contours that I want to check for
crossing. For this domain, overlap/touch is fine, but not crossing.
The following junit-formatted example show two LineStrings that
touch each other in (2 2). This is reported as a crossing by
LineString#crosses(LineString), but for my domain this is not a cross.
public void testCrosses() throws ParseException {
WKTReader r = new WKTReader();
LineString ls1 = (LineString) r.read("LINESTRING (1 2, 3 2)");
LineString ls2 = (LineString) r.read("LINESTRING (1 1, 2
2, 3 1)");
assertFalse(ls1.crosses(ls2));
}
Any tips to how I can check for crossing, but not touches like this?
Regards,
Tore Halset.
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