building footprint processing for downtown portland

gistfile1.js

var JSONStream = require('JSONStream'),
    fs = require('fs'),
    Terraformer = require('Terraformer');

var incoming = fs.createReadStream("./buildings.json", { encoding: "utf8" });
var outgoing = fs.createWriteStream("./processed.json", { encoding: "utf8" });

var stream = JSONStream.parse(['features', true]);

var downtown = new Terraformer.Polygon(
  [
    [
      [ -122.686858, 45.534251 ],
      [ -122.682910, 45.534431 ],
      [ -122.670207, 45.526194 ],
      [ -122.669606, 45.522195 ],
      [ -122.674541, 45.511851 ],
      [ -122.671623, 45.507099 ],
      [ -122.674413, 45.505745 ],
      [ -122.681408, 45.506136 ],
      [ -122.689605, 45.513204 ],
      [ -122.685657, 45.522045 ],
      [ -122.686772, 45.524270 ],
      [ -122.686858, 45.534251 ]
    ]
  ]
);

outgoing.write('{ "type": "FeatureCollection", "features": [');
outgoing.write("\n");

stream.on('data', function (data) {
  var primitive = new Terraformer.Primitive(data.geometry);
  if (primitive.within(downtown)) {
    outgoing.write(JSON.stringify(data) + ",\n");
  }
});

stream.on('end', function () {
  outgoing.write("] }\n");
  outgoing.end();
});

incoming.pipe(stream);