Clip Michigan to Land Area

[hodgesmr]

This pull request serves as an idea for the rest of the state files. I chose to start with Michigan because it illustrates the diff and would be good to solicit feedback.

The current geojson for Michigan renders into the bodies of water around the state. This makes for unexpected shapes when drawn. I noticed that the district geojson provided by @schwanksta in the 2016 files clipped to the land area. To get a state clipped to land, I created a union of all the MI districts, and then dissolved their geometries into fewer polygons.

Before:

After:

If this change is deemed desirable, I can follow the same process for the other states.

[ogtega]

Aren't the areas within bodies of water also part of the state's boundaries?

[hodgesmr]

@ogtega I believe so, and that's part of my question around the general "desirability" of the PR. Depending on your usecase you might want one or the other. Like, if you want to say if a point is "within" a state's jurisdiction, you probably do want to include bodies of water... but if you want to draw a map of the US with state lines, you might not expect the water to be included (this is what I was doing and noticed how weird Michigan and Wisconsin looked).

[konklone]

I think we'd likely be better off, as a project that intends to have authoritative data, to avoid weakening the authoritativeness of a piece of data in favor of aesthetic impact in some circumstances.

Even on Google Maps, they include water in the visible boundary:

Though if there's interest in maintenance, maybe we could maintain both for the several states that have significant water within their boundaries.

Just my thoughts - not trying to shut down discussion.

[schwanksta]

@konklone I get that argument. Like I said over in #10, I'm not sure I see the utility of a congressional districts repo containing state files either way, but if we want to maintain those (since geojson is nicer, and we can link to them individually), what about starting a new states repo with clipped and unclipped files?

[ogtega]

@schwanksta it only makes sense

[konklone]

@schwanksta This repository is/was intended to show the shapes of districts for everyone in the US Congress, and for senators that's their states. We also want the repository to be useful to folks who want to pull down the GeoJSON via permanent URLs -- we have this hooked up to GitHub Pages and CloudFlare so that they are downloadable from https://theunitedstates.io.

I think if another more reliable/maintained source offered consistent perma-URLs to GeoJSON for states or districts, we could refer to that source instead, though we'd at least need to maintain the URLs in place for a while, while we identified clients currently using the data and planned a deprecation schedule.