Identifying Parcels on Street Junction in QGIS

Question

I have the following shapefiles (click here to download them):

1. parcels polygon
2. parcels point
3. streets/row polygon
4. streets line

I use QGIS to manually identify polygon parcels with street corners (street junctions) on them. I would like to know if there is a plugin or algorithm to provide such a solution to identify all parcel polygons that are on street junctions. That is those polygons that are on the corner of the street line.

For example, the parcels mark in the red box below have corners. So, they are selected for export.

This could be done a manual visual inspection of the parcels. However, I am looking for an automated in QGIS.

Answer 1

In PostGIS, you could select the PIN code (I assume this is the unique ID for parcel?) where the parcel intersects more than one buffered street line (buffered far enough to cross the street):

SELECT sbuff.pin, sbuff.touch FROM 
    (SELECT b.pin, count(a.code) as touch
        FROM street_lines a, parcel_polygon b
        WHERE st_intersects(st_buffer(a.geom, 0.00015, 'endcap=flat'), b.geom) 
        GROUP BY b.pin) AS sbuff
    WHERE touch > 1

Giving:

pin         touch
2823059034  8
1423901050  2
1432700720  2
1423500560  2
1433200140  2
...

Note:

• This doesn't reproject the layers to UTM so dimensions are in decimal degrees - the 0.00015 approximates a 15m buffer;
• Performing st_intersects without a spatial index is super slow, better to create a new indexed buffer layer and use that.
• You probably want endcap=flat but should experiment.