[GIS] Converting Mapbox Vector Tiles To GeoJSON

mapboxnode-jsturfvector-tiles

I'm working on a project that needs to do some simple turf.js work on the client. I am using Mapbox to host my GeoJSON data. Mapbox serves the client this data as a vector tile set, which saves a lot on bandwidth and load times on the client for large datasets. Unfortunately turf.js only works with GeoJSON, not Mapbox Vector Tiles. As far as I know, there are two libraries that can convert vector tiles into GeoJSON: vt-geojson, and vector-tile-js. The problem with these libraries is that they are Node.js libraries, not browser javascript.

At this point it seems I have four options:

Convert one of these libraries to normal javascript (and spend time doing it)
Add Browserify to my project to convert it for me (and messy up my project)
Find some other javascript library that can do it for me (and maybe not find one)
Write my own library (and spend lots of time and effort)

I'm hoping that someone on here can help me with the third option, finding a JS library.

Best Answer

I think you're out of luck, there is no third option. I cannot claim this with 100% certainty, but I'm at the moment doing an extensive research about vector tiling, and in short MapBox vector tiles are optimized for presentation for their own rendering engine. So while open, it is more or less proprietary - and from this perspective it is probably best to stick closely to MapBox libraries (stability and quality when dealing with these vector tiles).

So I'd say it's best to stick with vt-geojson. But I think you could also open a feature request on Github. This sounds like a useful feature.

Related Solutions

Self-Hosting Mapbox Tiles – Guide to Self-Hosting Mapbox Vector Tiles

As pointed out by @Greg, instead of TileStream (my first attempt) you should use Tilelive to host your own vector tiles.

Tilelive isn't a server itself but a backend framework that deals with tiles in different formats from different sources. But it's based on Node.js so you can turn it into a server in a pretty straight-forward way. To read tiles from a .mbtiles source as exported by Mapbox Studio, you need the node-mbtiles tilelive module.

Side note: Current Mapbox Studio has a bug under Windows and OS X that prevents an exported .mbtiles file to show up at your chosen destination. Workaround: Just grab the latest export-xxxxxxxx.mbtiles file in ~/.mapbox-studio/cache.

I found two server implementations (ten20 tile server by alexbirkett and TileServer by hanchao) who both use Express.js as a web app server.

Here is my minimalistic approach which is loosely based on these implementations:

Install Node.js
Grab the node packages with npm install @mapbox/tilelive @mapbox/mbtiles express

Implement the server in the file server.js:

 var express = require('express');
 var http = require('http');
 var app = express();
 var tilelive = require('tilelive');
 require('mbtiles').registerProtocols(tilelive);

 //Depending on the OS the path might need to be 'mbtiles:///' on OS X and linux
 tilelive.load('mbtiles://path/to/osm_roads.mbtiles', function(err, source) {

     if (err) {
         throw err;
     }
     app.set('port', 7777);

     app.use(function(req, res, next) {
         res.header("Access-Control-Allow-Origin", "*");
         res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
         next();
     });

     app.get(/^\/v2\/tiles\/(\d+)\/(\d+)\/(\d+).pbf$/, function(req, res){

         var z = req.params[0];
         var x = req.params[1];
         var y = req.params[2];

         console.log('get tile %d, %d, %d', z, x, y);

         source.getTile(z, x, y, function(err, tile, headers) {
             if (err) {
                 res.status(404)
                 res.send(err.message);
                 console.log(err.message);
             } else {
               res.set(headers);
               res.send(tile);
             }
         });
     });

     http.createServer(app).listen(app.get('port'), function() {
         console.log('Express server listening on port ' + app.get('port'));
     });
 });

Note: The Access-Control-Allow-... headers enable cross-origin resource sharing (CORS) so webpages served from a different server may access the tiles.

Run it with node server.js

Set up the webpage using Mapbox GL JS in minimal.html:

 <!DOCTYPE html >
 <html>
   <head>
     <meta charset='UTF-8'/>
     <title>Mapbox GL JS rendering my own tiles</title>
     <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.4.0/mapbox-gl.css' rel='stylesheet' />
     <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.4.0/mapbox-gl.js'></script>
     <style>
       body { margin:0; padding:0 }
       #map { position:absolute; top:0; bottom:50px; width:100%; }
     </style>
   </head>
   <body>
     <div id='map'>
     </div>
     <script>
       var map = new mapboxgl.Map({
         container: 'map',
         center: [46.8, 8.5],
         zoom: 7,
         style: 'minimal.json'
       });
     </script>
   </body>
 </html>

Indicate the location of the tile source and style the layers with the following minimal.json:

 {
   "version": 6,
   "constants": {
     "@background": "#808080",
     "@road": "#000000"
   },
   "sources": {
     "osm_roads": {
       "type": "vector",
       "tiles": [
         "http://localhost:7777/v2/tiles/{z}/{x}/{y}.pbf"
       ],
       "minzoom": 0,
       "maxzoom": 12
     }
   },
   "layers": [{
     "id": "background",
     "type": "background",
     "paint": {
       "background-color": "@background"
     }
   }, {
     "id": "roads",
     "type": "line",
     "source": "osm_roads",
     "source-layer": "roads",
     "paint": {
       "line-color": "@road"
     }
   }]
 }

Serve the webpage and rejoice.

[GIS] Wrapping vector tiles generated by geojson-vt

I have very similar problem, except I try to use angular-leaflet-directive. So far i couldn't find much about it. However, please have a look at this example and the block itself. This may give you more ideas on how to link geojson-vt with leaflet.

Best Answer

Related Solutions

Self-Hosting Mapbox Tiles – Guide to Self-Hosting Mapbox Vector Tiles

[GIS] Wrapping vector tiles generated by geojson-vt

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