# How to calculate distance to polygon edge to compute building setbacks?

I'm trying to calculate building setbacks using building footprint data. A building setback is the distance between a building and the edge of the lot line. (You can distinguish this further—garage setback and structure setback, but I won't complicate things.) The image below (red lines) shows the distance I am trying to get for one of the blocks as an example.

I have no idea how to start this. I think I need to turn the footprint and parcel polygons into polylines and break at vertices? I want to use the street center-line (green) as a sort of magnet so that the distance is calculated to the front of the lot instead of the back or side. I can ignore corner lots for the time being.

BTW, the parcels are also dissolved so it is just block structure (pic below). That means I just need to find the shortest distance between the footprint polygon and the edge of the block polygon.

If anyone has any clue, please let me know! This is for a class project. (And I'm using ArcGIS and QGIS.)

• There was a similar post here which might be of some help. Commented Feb 17, 2015 at 11:08