Rotating point layer according to line layer in QGIS

Question

I got two layers: (1) a line layer with water pipelines and (2) a point layer that shows hydrants and so forth. The points are located, mostly, on the line layer.

For the symbology of the hydrants i want to use a simple marker half_square / rectangle that should be rotated 90° to the line layer.

My approach would be to use an expression for the rotation, but i have no idea how that expression has to look.

Answer 1

1. Find the nearest line using overlay_nearest
2. Buffer the point and intersect the buffer with the line to cut out a short segment of the line
3. Find the angle of this using line_interpolate_angle

With this expression:

line_interpolate_angle(
geometry:=intersection(buffer(geometry:=$geometry, distance:=100, segments:=3),
overlay_nearest(layer:='railways', expression:=$geometry)[0]), distance:=20)+90

You probably need to play around with the distances to get the best result.

zxcxz