examples/leaflet_vector_query_distance.html

<!DOCTYPE html>
<html>
  <head>
    <title>Leaflet vector query distance example | CartoDB.js</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <link rel="shortcut icon" href="http://cartodb.com/assets/favicon.ico" />
    
    <style>
      html, body, #map {
        height: 100%;
        padding: 0;
        margin: 0;
      }
    </style>

    <link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.6.2/leaflet.css" />
<!--[if lte IE 8]>
    <link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.6.2/leaflet.ie.css" />
<![endif]-->

  </head>  
  <body>
    <div id="map"></div>

    <script src="http://cdn.leafletjs.com/leaflet-0.6.2/leaflet.js"></script>

    <!-- include cartodb.js library -->
    <script src="http://libs.cartocdn.com/cartodb.js/v3/cartodb.core.js"></script>
    <script>

      function main() {

        var map = L.map('map', { 
          zoomControl: false,
          center: [40.78151171, -73.94959818,0], 
          zoom: 13
        })

        var sql = new cartodb.SQL({ user: 'examples', format: 'geojson' });

        L.tileLayer('http://tile.stamen.com/toner/{z}/{x}/{y}.png', {
          attribution: 'Stamen'
        }).addTo(map);


        map.on('click', function(e) {
          show_wifi_near(e.latlng, 500); //500 meters
        });

        var geojsonMarkerOptions = {
          radius: 3,
          fillColor: "#ff7800",
          color: "#000",
          weight: 1,
          opacity: 1,
          fillOpacity: 0.8
        };

        var wifiPoints = L.geoJson(null, {
          pointToLayer: function (feature, latlng) {
            return L.circleMarker(latlng, geojsonMarkerOptions);
          }
        }).addTo(map);


        function show_wifi_near(position, radioMeters) {
          var vars = {
            lat: position.lat,
            lon: position.lng,
            radio: radioMeters
          }
          sql.execute("select * from nyc_wifi where ST_Distance(the_geom::geography, ST_SetSRID(ST_MakePoint({{lon}}, {{lat}}), 4326)::geography) < {{radio}}", vars).done(function(geojson) {
              wifiPoints.addData(geojson);
          });
        }


      }

      window.onload = main;

    </script>

  </body>
</html>