WWSD #11: Mapbox-gl + d3 SVG overlay by enjalot

This is a simple setup of Leaflet (via Mapbox) with d3 to show dots on a map. This can serve as a base for many interesting geographically based visualizations

Nice overview of using d3 + Leaflet. I found this slightly simpler to use than Mike’s classic post.

Built with blockbuilder.org

forked from enjalot‘s block: dots on a map: setup-gl

index.html

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
  <script src="//d3js.org/topojson.v1.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js'></script>
  <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.css' rel='stylesheet' />

  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    #map { 
      position:absolute; 
      width: 100%;
      height: 100%;
    }
    svg {
      position: absolute;
      width: 100%;
      height: 100%;
    }
  </style>
</head>

<body>
  <div id="map"></div>
  <script>
  
    mapboxgl.accessToken = 'pk.eyJ1IjoiZW5qYWxvdCIsImEiOiJjaWhtdmxhNTIwb25zdHBsejk0NGdhODJhIn0.2-F2hS_oTZenAWc0BMf_uw'
    
    //Setup mapbox-gl map
    var map = new mapboxgl.Map({
      container: 'map', // container id
      style: 'mapbox://styles/enjalot/cihmvv7kg004v91kn22zjptsc',
      center: [-0.1,51.5119112],
      zoom: 13.5,
      
    })
    map.scrollZoom.disable()
    map.addControl(new mapboxgl.Navigation());

    // Setup our svg layer that we can manipulate with d3
    var container = map.getCanvasContainer()
    var svg = d3.select(container).append("svg")

    // we calculate the scale given mapbox state (derived from viewport-mercator-project's code)
    // to define a d3 projection
    function getD3() {
      var bbox = document.body.getBoundingClientRect();
      var center = map.getCenter();
      var zoom = map.getZoom();
      // 512 is hardcoded tile size, might need to be 256 or changed to suit your map config
      var scale = (512) * 0.5 / Math.PI * Math.pow(2, zoom);

      var d3projection = d3.geo.mercator()
        .center([center.lng, center.lat])
        .translate([bbox.width/2, bbox.height/2])
        .scale(scale);

      return d3projection;
    }
    // calculate the original d3 projection
    var d3Projection = getD3();
    
    var path = d3.geo.path()
  
    var url = "//enjalot.github.io/wwsd/data/UK/london_stations.topojson";
    d3.json(url, function(err, data) {
      var points = topojson.feature(data, data.objects.london_stations)
      //console.log(data[0], getLL(data[0]), project(data[0]))
      var dots = svg.selectAll("circle.dot")
        .data(points.features)
      
      dots.enter().append("circle").classed("dot", true)
      .attr("r", 1)
      .style({
        fill: "#0082a3",
        "fill-opacity": 0.6,
        stroke: "#004d60",
        "stroke-width": 1
      })
      .transition().duration(1000)
      .attr("r", 6)
      
      function render() {
        d3Projection = getD3();
        path.projection(d3Projection)
        
        dots
        .attr({
          cx: function(d) { 
            var x = d3Projection(d.geometry.coordinates)[0];
            return x
          },
          cy: function(d) { 
            var y = d3Projection(d.geometry.coordinates)[1];
            return y
          },
        })
      }

      // re-render our visualization whenever the view changes
      map.on("viewreset", function() {
        render()
      })
      map.on("move", function() {
        render()
      })

      // render our initial visualization
      render()
    })

    
  </script>
</body>