Creating line between point layer and line layer in QGIS

Question

My goal is to create a line layer that is derived from the distance between a point layer and a line layer. An example could be using a line layer representing a road and a point layer representing a home or telephone pole.

I would like to create a vector line that extends from the road line layer to the point layer. Is there a Plugin for this?

Answer 1

You can also use QGIS expressions to crease such lines. There are two ways to do that:

1. Use geometry generator for visualization purpose, without creating a new layer. For that, add a new symbol layer in the style panel and set it to Geometry Generator / Linestring (see screenshot below).
2. Create actual geometries on a new layer: Menu Processing / Toolbolx / Geometry by expression.

In both cases, use the expression on the points layer, use the same expression (on line 6, replace 'line' with the name of your line-layer). Be aware that the overlay_nearest function is available since QGIS 3.16:

make_line (
    $geometry, 
    closest_point (
        array_first (
            overlay_nearest (
                'line' , 
                $geometry
            )
        ), 
    $geometry
    )
)

The screenshot illustrates the first version of using the expression:

Answer 2

You can achieve this using a virtual layer

go to the menu Layer > Add Layer > Add/Edit Virtual Layer... and enter the query

select p.id, l.id, 
       min(st_distance(p.geometry, l.geometry)) dist, 
       ST_ShortestLine(p.geometry, l.geometry) geometry
from myPointLayer p, myLineLayer l
group by p.id
order by st_distance(p.geometry, l.geometry) asc

The group by will ensure we get a single row for each row in layer1. Because we order by distance and keep the min, the group by will retain the 1st entry, i.e. the nearest one.