Automatically snapping points to line ends on two separate layers?

Question

I have US interstate ramp end location data points that I need to match road network data. All the points are off by a few meters as they were collected in the field. I am hoping there is a way to automatically match/snap all the points to the end nodes of the ramps if within 20 meters. I can't do it manually as there are over 30,000 points. Road network and ramp points are different layers.

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EDIT: The blue lines are the on/off ramps of an interstate. The red points are the field collected location of the end of the off ramp. I need the red points to auto snap on to end of the off ramp.

After thinking about this and the goal all I really need is the start and end points for each ramp and a way to differentiate between them. I'll ask in a different question. However for clarity sake I thought I would post what I originally was requesting.

I haven't found any information on how to automatically snap points to line ends in bulk. Anything I've found that was similar didn't translate.

Answer 1

You may run the following code from the Python Console:

searching_dist = 20 # Set it as you want

lines = QgsMapLayerRegistry.instance().mapLayersByName('line')[0] # Replace 'line' with the name of the line layer
points = QgsMapLayerRegistry.instance().mapLayersByName('points')[0] # Replace 'points' with the name of the point layer

cr = points.crs()
dist_calc = QgsDistanceArea()
dist_calc.setSourceCrs(cr)
dist_calc.setEllipsoid(cr.ellipsoidAcronym())
dist_calc.setEllipsoidalMode(cr.geographicFlag())

# This layer contains all the points created along the line (it isn't an output)
crs = points.crs().toWkt()
temp_pts = QgsVectorLayer('Point?crs='+ crs, 'temp_pts' , 'memory')
prov = temp_pts.dataProvider()

tmp_points = {}
index = QgsSpatialIndex()
for line in lines.getFeatures():
    line_geom = line.geometry()
    (first_line_point, end_line_point) = (line_geom.interpolate(0).asPoint(), line_geom.interpolate(line.geometry().length()).asPoint())
    pt1 = QgsFeature()
    pt1.setGeometry(QgsGeometry.fromPoint(first_line_point))
    (result, feat) = prov.addFeatures([pt1])
    tmp_points[feat[0].id()] = feat[0]
    index.insertFeature(feat[0])
    pt2 = QgsFeature()
    pt2.setGeometry(QgsGeometry.fromPoint(end_line_point))
    (result, feat) = prov.addFeatures([pt2])
    tmp_points[feat[0].id()] = feat[0]
    index.insertFeature(feat[0])

for point in points.getFeatures():
    geom = point.geometry()
    nearest = index.nearestNeighbor(geom.asPoint(), 1)
    tmp_pt_geom = tmp_points[nearest[0]].geometry()
    dist = dist_calc.measureLine(geom.asPoint(), tmp_pt_geom.asPoint())
    if dist <= searching_dist:
        points.dataProvider().changeGeometryValues({point.id(): tmp_pt_geom})
points.triggerRepaint()

For get it working, you only need to preliminary load the point and line layers in the Layers Panel and then type their names where needed (I left a comment in the code above). Furthermore, you need to specify a searching distance (I used 20 meters, set it as you want).

Finally, the above code will directly edit the geometries within the point layer, so remember to create a backup copy of your data before trying it.

As an example, starting from this situation:

you will get this result:

and, zooming more on it (as you did in your original question):

EDIT

If you want to snap the points by considering the final line nodes only, you may use this slightly edited code:

searching_dist = 20 # Set it as you want

lines = QgsMapLayerRegistry.instance().mapLayersByName('line')[0] # Replace 'line' with the name of the line layer
points = QgsMapLayerRegistry.instance().mapLayersByName('points')[0] # Replace 'points' with the name of the point layer

cr = points.crs()
dist_calc = QgsDistanceArea()
dist_calc.setSourceCrs(cr)
dist_calc.setEllipsoid(cr.ellipsoidAcronym())
dist_calc.setEllipsoidalMode(cr.geographicFlag())

# This layer contains all the points created along the line (it isn't an output)
crs = points.crs().toWkt()
temp_pts = QgsVectorLayer('Point?crs='+ crs, 'temp_pts' , 'memory')
prov = temp_pts.dataProvider()

tmp_points = {}
index = QgsSpatialIndex()
for line in lines.getFeatures():
    line_geom = line.geometry()
    end_line_point = line_geom.interpolate(line.geometry().length()).asPoint()
    pt1 = QgsFeature()
    pt1.setGeometry(QgsGeometry.fromPoint(end_line_point))
    (result, feat) = prov.addFeatures([pt1])
    tmp_points[feat[0].id()] = feat[0]
    index.insertFeature(feat[0])

for point in points.getFeatures():
    geom = point.geometry()
    nearest = index.nearestNeighbor(geom.asPoint(), 1)
    tmp_pt_geom = tmp_points[nearest[0]].geometry()
    dist = dist_calc.measureLine(geom.asPoint(), tmp_pt_geom.asPoint())
    if dist <= searching_dist:
        points.dataProvider().changeGeometryValues({point.id(): tmp_pt_geom})
points.triggerRepaint()