[GIS] Splitting line at point positions using QGIS

linepointqgissplittingvector

I have a polyline and I have two points on the polyline.

I would like to know if there is a tool or script that I could use to split my original polyline into 3 polylines? (Starting point to point A, Point A to B and B to ending point of the polyline)?

I am looking for an automatic process rather splitting the line manually.

Best Answer

QGIS won't do this natively to the best of my knowledge. However, you can use GRASS from within QGIS, and this thread looks like exactly what you want. I haven't tested this, but it all makes sense. Credit of course goes to the folks in that thread. First, you would import your data into GRASS then:

dump the coordinates to a text file (v.out.ascii) then loop thru that file, and feed the coords to v.edit, like so: v.out.ascii out=points.txt while read x y; do v.edit tool=break coord=$x,$y cat=0-99999 done < points.txt

Note the caveat that your points must be exactly on the line.

Or, even simpler in a bash environment:

v.out.ascii format=point in=pts --q | cut -d'|' -f1,2 | tr '|' ',' | while read COOR; do v.edit map=line tool=break coords=$COOR; done

Related Solutions

[GIS] QGIS or Postgis – How to split polylines with a point layer

You can see solutions using GRASS here

There's also another option with Spatialite. The newest version 4.0 has a function LinesCutAtNodes() which does what you want. You feed it a linestring geometry and a point geometry, and it returns a linestring split wherever a point exactly intersect a vertex on the line. The points have to intersect vertices on the line, so you should do snap() first to get the points to exactly intersect the line vertices.

Using ArcObjects – Splitting zAware Polyline by Points in C#

This code works for me:

public void SplitPolylineFeature(IFeature pPolylineFeature, IPointCollection pSplitPointCollection, IFeatureClass pFeatureClass)
{
    //split the feature, each split makes a new part
    IEnumVertex pEnumVertex = pSplitPointCollection.EnumVertices;
    IPolycurve2 pPolyCurve = pPolylineFeature.Shape as IPolycurve2;
    IEnumSplitPoint pEnumSplitPoint = pPolyCurve.SplitAtPoints(pEnumVertex, true, true, -1);
    object Missing = Type.Missing;

    if(pEnumSplitPoint.SplitHappened)
    {
        //new geocoll for polycurve
        IGeometryCollection pGeometryCollection = pPolyCurve as IGeometryCollection;

        //loop through the parts of the split polyline
        for(int intPartCount = 0; intPartCount < pGeometryCollection.GeometryCount; intPartCount++)
        {
            IGeometryCollection pLineGeoColl = new PolylineClass();
            IZAware zAware1 = (IZAware)pLineGeoColl;
            zAware1.ZAware = true;

            IGeometry pGeometry = pGeometryCollection.get_Geometry(intPartCount);

            pLineGeoColl.AddGeometry(pGeometry, ref Missing, ref Missing);

            IFeature pFeature = pFeatureClass.CreateFeature();

            pFeature.Shape = pLineGeoColl as IGeometry;
            pFeature.Store();
        }
    }
    pPolylineFeature.Delete();
}

All I did was make pLineGeoColl ZAware.

Best Answer

Related Solutions

[GIS] QGIS or Postgis – How to split polylines with a point layer

Using ArcObjects – Splitting zAware Polyline by Points in C#

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