How the create the nearest point on a line layer in QGIS?

Question

How can I generate a projection of points on the nearest line?

I have a layer with several points and I have another layer with several lines. And I want to generate a projection of these points but creating points in these projections.

I found this picture online that illustrates what I want to do:

I want to create this projection but also create a point in the final projection (in the line) as a new layer with these points.

Is not the nearest line the one that passes through the point? — Gabriel De Luca, Mar 09 '20 at 17:16
I don't know exactly. Because I want the projective point in the nearest line. — ZacariasSatrustegui2, Mar 09 '20 at 18:20
are the lines running from the point to your vertical line already created in your case? if yes, then is your goal to create a point where those lines intersects? and if yes you can use Line intersections from the processing toolbox. If not please explain what you mean. — B-C B., Mar 09 '20 at 18:41
yes, but first you have to create the vertical lines. But I want to learn with python and not with toolbox. — ZacariasSatrustegui2, Mar 10 '20 at 06:45
In Python (PyQgis)), the solution of Drawing perpendicular lines in PyQGIS? works also in QGIS 3.x — gene, Mar 10 '20 at 09:48
But in that question, you know the line, but in my case I don't know the line, you just have a layer of lines and I want to find the nearest line and then the projective point. — ZacariasSatrustegui2, Mar 10 '20 at 10:04
use the solution of Finding the nearest line to a point in QGIS,but Not Work for that — gene, Mar 10 '20 at 10:41

Babel · Answer 1 · 2020-12-30T20:20:57.453

If you don't mind using expressions, you can achieve this with geometry generator (for visualization purpose only) or with Menu Processing / Toolbox / Geometry by expression (if you want to create a new layer with the nearest points on the line). In both cases, the expression remains the same.

Let's suppose you have the same setting as on the screenshot below: a red line (layer named line) and the red points. To demonstrate it with geometry generator: On the points layer, you add a symbol layer (click the green + symbol), than set it to Geometry generator, as Geometry type select points and paste the following expression. It generates the blue points on the screenshot (I added the black lines connecting red and corresponding nearest blue point on the line for easier identification only):

closest_point (   
    geometry ( 
        get_feature_by_id ( 
            'line' , 1 
        ) 
    ) , 
    $geometry
)

How the create the nearest point on a line layer in QGIS?

1 Answers1