I have a few election district boundaries layers across several different elections, and I am trying to ascertain whether/how much the district boundaries have changed over time.

They are labeled with an ID but there is no guarantee that features with the same ID are in fact the same entity.

My rough idea is that I should compare the shapes of the boundaries across years, and if their overlap is sufficiently large (say 90%), then I can consider them the same entity.

I tried to google for an answer but being a novice I guess I just don't know the right keywords to search and couldn't find a way to achieve it.

Here is a screenshot of what they look like: enter image description here

  • Do you have multiple data sources for each election? Do they have the same geometry? – wfgeo Mar 16 at 20:01
  • The shape files all come from the same government office and they are all polygons. They are using the same projection. – Glen Ng Mar 16 at 20:08
  • And there is truly no common identifier? Not even an external metadata document which ties them together? Also, are the polygons completely identical between datasets? Could you add a picture of two different years? – wfgeo Mar 16 at 20:29
  • There are identifier, and say district A01 is always be in the same larger region A, but A01 in 2012 may or may not be the same district as A01 in 2016, going from exactly the same (most cases) to zero overlap (relatively rare). – Glen Ng Mar 17 at 6:05

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