tile-reduce + cheap-ruler example

index.js

var tileReduce = require('tile-reduce');
var path = require('path');

tileReduce({
  zoom: 14,
  map: path.join(__dirname, '/process.js'),
  sources: [
    {name: 'ways', mbtiles: 'ways.mbtiles')}
  ]
});

process.js

var createRuler = require('cheap-ruler');

module.exports = function(data, tile, writeData, done) {
  var ruler = createRuler.fromTile(tile[1], tile[2]);
  var length = 0;
  data.ways.ways.features.forEach(function(way){
    length += ruler.lineDistance(way.geometry.coordinates);
  });
  done(null, length);
};