Using vector-tile-js to get water polygons as geojson tiles

README.md

Using vector-tile-js to get water polygons as geojson tiles

Usage

npm install
node get-geojson.js <tile address>

<tile address> is a set of tile coordinates passed in as a string in the form [x,y,z] e.g. node get-geojson.js "[958, 1696, 12]"

get-geojson.js

// SPIT OUT A NAMED GEOJSON FILE FOR EACH INPUT TILE ADDRESS

var fs = require('fs');
var request = require('request');
var turf = require('turf');
var Protobuf = require('pbf');
var VectorTile = require('vector-tile').VectorTile;

var bigTile = process.argv[2];
//var outDir = process.argv[3];
var mbToken = 'sk.eyJ1IjoibGFuZHBsYW5uZXIiLCJhIjoiY2ltcjB0MmozMDB0MHY5a2t5c2Fsb3Q0diJ9.3qyTzT995P_Fo1fJ2tyr6A';
var mbUrlBase = 'http://a.tiles.mapbox.com/v4/mapbox.mapbox-streets-v7/';
var mbUrlSuffix = '.vector.pbf?access_token=' + mbToken;

var x = JSON.parse(bigTile)[0];
var y = JSON.parse(bigTile)[1];
var z = JSON.parse(bigTile)[2];

var getTile = request({url: mbUrlBase + z + '/' + x + '/' + y + mbUrlSuffix, gzip: true, encoding: null}, function (error, response, body) {
  if (error) {
    console.error('encountered error', error instanceof Error ? error.stack : error);
  } else if (response.statusCode === 429) {
    console.log('error 429');
  } else if (response.statusCode !== 200) {
    console.error('non-200 status code: ' + response.statusCode);
  } else {
    var buf = new Protobuf(body);
    var vt = new VectorTile(buf);
    var layer = vt.layers['water'];
    if (layer && layer.length > 0) {
      var waterSet = {"type":"FeatureCollection","features":[]};
      for (var i = 0; i < layer.length; i++) {
        var feature = layer.feature(i).toGeoJSON(x,y,z);      
        waterSet.features.push(feature);
      }
      fs.writeFile('osm_water_' + x + '_' + y + '_' + z + '.geojson', JSON.stringify(waterSet), 'utf-8');
      console.log('got tile ' + bigTile);
    }
    else {
      console.log('no water features at tile {' + z + '}/{' + x + '}/{' + y + '}')
    }
  }
});

getTile;

package.json

{
  "name": "water",
  "version": "2.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "vtcraghead@gmail.com",
  "license": "ISC",
  "dependencies": {
    "pbf": "^1.3.5",
    "request": "^2.69.0",
    "turf": "^2.0.2",
    "vector-tile": "^1.2.0"
  }
}