Select features in a polygon that covered the most by features of another polygon layer QGIS

Question

I am working in QGIS. I have 2 polygon layers,

1. One layer is the parcel polygons layer for a county called "Parcel"
2. The other layer is the building footprints polygon layer for the same county called "BuildingFootprint"

The building footprints features overlap multiple parcel polygons. I want to select the parcel polygons that the building footprint overlaps the most (majority). So for example, if I have two parcel polygon features overlapped by one building footprint feature, I want to select the parcel polygon that is covered by 90% of the building footprint feature and not select the parcel polygon feature that is covered by 10% of the building footprint.

Uncovering a way to select the parcel that is covered by majority of the building footprint will then allow me to join that particular parcel feature's number to the building footrpint feature's attribute table.

Answer 1

QGIS 3.2

(0) Prepared a test dataset:

• Parcels polygon layer (3 features): unique id field= PARCELNO
• BuildingFootprints layer (3 features): unique id field= Florida_ID

(1) Join attribute by location tool (QGIS processing toolbox | Vector general)

Make sure to choose Create separate feature for each located feature (one-to-many) option. This is the important tool newly available in QGIS 3.2 to produce all combinations of polygon overlay.

(2) Now you will have Joined layer layer with Florida_ID and PARCELNO fields. Then open the attribute table of this Joined layer and start the Field Calculator.

(2a) First, calculate overlapping percentage for each row.

Expression is:

area(intersection($geometry, geometry(get_feature('Parcels', 'PARCELNO', "PARCELNO")))) 
/ area($geometry) * 100

(The first line is calculating the area, while the second line / area($geometry) * 100 is just turning it into the percentage.)

(2b) And add another field to pick the polygon which overlapping percentage is the biggest among the Building group.

Its expression is "overlap" = maximum( "overlap", group_by:= "Florida_ID")

(3) Lastly, select the value 1 from the above calculated field (Best). They are the combination you need, I mean, the "most overlapping" Building-Parcels polygons. (Or, you may simply delete Best=0 rows).