Projecting polygons into polyline

Question

I have a polygon layer and a polyline layer. I want to project the polygons onto the polyline like I show in the following images.

The first image shows the features I have.

The second image shows the projection lines (red dashed lines) as I think the concept might work.

The third image shows the resulted segments of the polyline as I expect them to be.

I don't know if this can help, the cells are from a raster grid layer and the polylines represent a road.

It is like the shadow of the polygons cast on the polyline using perpendicular lines to the polyline from the vertices of the polygon. However, the perpendicular is just a concept. I don’t know how it could better work.

I can use: QGIS version 3.10.1-A Coruña Or ArcGIS 10.4.1 for Desktop

Answer 1

QGIS Solution

Let's assume there are two layers 'squares' (green) and 'lines' (blue) with its corresponding attribute tables accordingly, see image below.

Step 1. Proceed with the "Extract vertices" (Apply additionally the "Delete duplicate geometries" or the "Remove duplicate vertices" if needed)

Step 2. By means of a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer... use a query query with ST_ClosestPoint()

SELECT v.id, sv.Name, ST_ClosestPoint(l.geometry, v.geometry) AS geom
FROM "vertices" AS v, lines AS l

Step 3. Proceed with "Points to path". Do not forget about the 'Order field'

Step 4. Proceed with the "Buffer". Do not forget about 'End cap style' and 'Join Style'

Step 5. Proceed with the "Difference" or as was mentioned in comments apply the "Intersection".

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References:

• Where/How can I enter the code for a Virtual Layer?

Answer 2

ArcGIS Solution using ArcPy

You can:

• Generate Near Table to find coordinates to nearest line from each polygon
• Move each polygon to that coordinate with da.UpdateCursor
• Clip the line using polygons as clip features

import arcpy

arcpy.env.workspace = r'C:\GIS\Somedatabase.gdb' #Change
lines = 'polyline' #Change
polygons = 'squares' #Change. WILL BE ALTERED SO BACKUP YOUR DATA BEFORE BEFORE EXECUTING CODE
output_lines = 'newlines123' #Change

arcpy.GenerateNearTable_analysis(in_features=polygons, near_features=lines, out_table='neartable', location=True, closest=True) #Find nearest line coordinates
d = {oid:[x,y] for oid,x,y in arcpy.da.SearchCursor('neartable',['IN_FID','NEAR_X','NEAR_Y'])} #Store in dictionary of OID:coordinates

with arcpy.da.UpdateCursor(polygons,['OID@','SHAPE@X','SHAPE@Y']) as cursor: #Move each polygon
    for row in cursor:
        row[1], row[2] = d[row[0]]
        cursor.updateRow(row)

arcpy.Clip_analysis(in_features=lines, clip_features=polygons, out_feature_class=output_lines)