shannonmcharg
commented
3 years ago We want to get to a point where you can input your address and out pops a list of your candidates and ballot questions. @robkorobkin did some work figuring out how to replicate the state's district lookup tool in this site: http://groundgamer.org/
Can we replicate this on Maine Ballot?
Details from Rob about what he did below:
Nothing's minified, and there are comments and variable / function names that actually make sense, so whoever's coding for you should hopefully have an okay time reading it?
If you're curious how I handle going from an address to identifying the legislative district for that address, here's the technobabble:
So, the first thing I did was get the GIS lat/lon boundary points of each legislative region out of the State's GIS archive, which I then wrote a script to convert to JSON: http://groundgamer.org/data/turfs/senate_districts.js http://groundgamer.org/data/turfs/house_districts.js
For data files, they're actually not that hard to read. Just a bunch of (lat,long) coordinates that pin out the boundaries of each legislative district.
Then, since I now had the districts as JSON, it wasn't all that hard to feed them into the Google Maps JS SDK to create the district overlay polygons that you see when you load the app.
The UI for the app contains a little form that takes an address, and then pings it to Google's geocode API, which spits back the lat/lon of the target address: https://maps.googleapis.com/maps/api/geocode/json?address=85%20Fessenden%20St,%20Portland,%20ME%2004103&key=AIzaSyDxvSHxYEcCAseWokSJ4HyTE0g9xA0IH0w
Then, this is where the magic happens, there's a little javascript function that iterates through the list of displayed polygons to see if each polygon contains the specified location. Ie: it goes through all the districts (which are now loaded onto the map) and checks to see if your address (which you just got back from the API) is contained within it.
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Hopefully this won't be too hard for you guys to implement into your thing.
Basically all you should need to do so is:
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Those JSON files that lay out the districts (takes some string manipulation to load them into RAM).
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A way to get the lat/lon of the point you're looking for. That api endpoint above is super useful for all sorts of stuff.
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And then a function that can take a polygon and a point (address) and can see if the point is in the polygon (legislative district) or not. The GoogleMaps JS SDK offers this as a global static utility function. But I mean, people have been trying to do that since Euclid was born in 365 BCE, there's got to be a bunch of libraries out there that can do that.
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Hope this helps.
All the stuff for GroundGamer.org is here: https://github.com/OpenMaine/GroundGamer_maine
Need to decide whether it's worth keeping and if we can make improvements with the data we have.