Projecting points on line and calculating distance from line start

Question

I have

• a vector layer with a number of points which correspond to magnetic targets
• axis retrieved from AutoCAD

The task is to project the points on the axis and then calculate the distance of each projected point from the start of the axis. Ideally, I would like the calculated distance to be on the same table as the points so I can know which point each distance refers to.

Moreover, it would be nice to know the perpendicular distance of each point from the reference axis. A picture of the above problem is also presented below.

Answer 1

Start the Field Calculator on your point layer's attribute table.

Create a new field by an expression below:

line_locate_point(geometry:=geometry(get_feature('NaMy_FSR', 'id', '1')), point:=$geometry)

Assuming:

• Your line layer name is : NaMy_FSR
• The line has an attribute value 1 in the 'id' field. (You can use any field to distinguish the line).

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[EDIT]

As to the distance the perpendicular distance of each point from the reference axis;

Not sure if this works, but will you try:

distance(closest_point(geometry(get_feature(‘NaMy_FSR’, ‘id’, ‘1’)), geometry), $geometry)

[revision]

distance(closest_point(geometry(get_feature(‘NaMy_FSR’, ‘id’, ‘1’)), $geometry), $geometry)