leaflet.js

Open-source mobile-friendly maps

about me

Ryan Ohs

Phoenix Web Group
Waverly, Nebraska

var map = L.map('map').setView([51.505, -0.09], 13);

L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
    attribution: '&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
}).addTo(map);

L.marker([51.5, -0.09]).addTo(map)
    .bindPopup('A pretty CSS3 popup. 
 Easily customizable.')
    .openPopup();

why leaflet?

Google Maps for Business costs $10,000/yr
Easy to use API
Lightweight

64K (vs 700K for OpenLayers)

Desktop and mobile support
Retina display support with high-dpi tiles
Currently at version 0.7.2

Started in 2010
Over 3000 commits and 157 contributers

what is openstreetmap?

Wikipedia for maps
Data has open license
User editable
1.5 million editors (doubling every year)
> 2 trillion data points

OSM vs Google

Comparison tool

http://flink.com.au/tips-tricks/27-reasons-not-to-use-google-maps

Getting map tiles for free

OpenStreetMap

Free but limited capacity
Can’t use in distributed mobile apps
http://wiki.openstreetmap.org/wiki/Tile_usage_policy

MapQuest Open license

Free, open license, requires attribution
For heavy usage (>4000 tiles/sec), contact them first
JPEG

MapBox

Free tier
No satellite imagery

Commercial Options

CloudMade

Original creator of Leaflet
$30 per 1 million tiles

MapBox (Lead dev now works here)

Free, then starting at $5/mo

Roughly $30 per 900,000 tiles

Also supports making your own tiles and layers

Big list at http://wiki.openstreetmap.org/wiki/Commercial_OSM_Software_and_Services

Tiles and zooming

http://{s}.tile.osm.org/{z}/{x}/{y}.png

20 zoom levels

0 = whole world
13 = a town
19 = 1 ft/px
Each level is about double the previous

Tiles are 256 x 256px PNG images
Approximately 15 tiles in a “map view”

getting started

Link to javascript and stylesheet

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.2/leaflet.css" />
<script src="http://cdn.leafletjs.com/leaflet-0.7.2/leaflet.js"></script>

Add a map div. Give it a height.

<div id="map" style="height: 600px"></div>

Initialize the map.

var map = L.map('map').setView([51.505, -0.09], 13);

Add a map tile layer

L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
    attribution: '© <a href="http://osm.org/copyright">
OpenStreetMap</a> contributors'
}).addTo(map);

mobile setup

Full screen support

body {
    padding: 0;
    margin: 0;
}
html, body, #map {
    height: 100%;
}

Disable automatic scaling

<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />

Initialize map (no coordinates here)

 var map = L.map('map');

L.tileLayer('map url', {
    attribution: 'attribution line',
    maxZoom: 18
}).addTo(map);

Geolocation

Zoom to the user's current position

 map.locate({setView: true, maxZoom: 16});

Continue initialization after success

function onLocationFound(e) {
    var radius = e.accuracy / 2;
    L.marker(e.latlng).addTo(map)
        .bindPopup("You are within " + radius + " meters from this point").openPopup();
    L.circle(e.latlng, radius).addTo(map);
}

map.on('locationfound', onLocationFound);

Handle error or permission denied

 function onLocationError(e) {
    alert(e.message);
}

map.on('locationerror', onLocationError);

Markers

Consist of an image and a shadow

 var appleIcon = L.icon({
    iconUrl: "../lib/images/apple.png",
    shadowUrl: "../lib/images/square-shadow.png",
    iconSize:     [32, 37],
    shadowSize:   [51, 37],
    iconAnchor:   [16, 37],
    shadowAnchor: [17, 37],
    popupAnchor:  [0, -37]
});
 
L.marker([51.5, -0.09], {icon: appleIcon}).addTo(map);

Creating Markers

Lots of free icons available online

Maps Icon Collection (CC BY SA 3.0)

Font-Awesome Markers (MIT)

Custom icons need custom shadow shapes

Google Maps Icon Shadowmaker

MArker Anchors

 iconSize:     [32, 37],
 shadowSize:   [51, 37],
 iconAnchor:   [16, 37],
 shadowAnchor: [17, 37],
 popupAnchor:  [0, -37]

Popups

Popups can be bound to a coordinate, marker, or shape.

marker.bindPopup("<b>Hello world!</b><br>I am a popup.").openPopup();
L.popup()
 .setLatLng([51.5, -0.09])
 .setContent("I am a standalone popup.")
 .openOn(map);

Shapes

Circles
Polygons
Lines
Paths

var circle = L.circle([51.508, -0.11], 500, {
    color: 'red',
    fillColor: '#f03',
    fillOpacity: 0.5
}).addTo(map);

var polygon = L.polygon([
    [51.509, -0.08],
    [51.503, -0.06],
    [51.51, -0.047]
]).addTo(map);

Layers

Two types:

Base layers - only one can be visible
Overlays - markers, geoJSON, etc.

Add default layers to the map initialization:

 var map = L.map('map', {
    center: new L.LatLng(40.82,-96.65),
    zoom: 10,
    layers: [streets, cities]
});

Add a Layers Control object to the map:

 L.control.layers(baseMaps, overlayMaps).addTo(map);


        var littleton = L.marker([39.61, -105.02]).bindPopup('This is Littleton, CO.'),
    denver    = L.marker([39.74, -104.99]).bindPopup('This is Denver, CO.'),
    aurora    = L.marker([39.73, -104.8]).bindPopup('This is Aurora, CO.'),
    golden    = L.marker([39.77, -105.23]).bindPopup('This is Golden, CO.');
var cities = L.layerGroup([littleton, denver, aurora, golden]);

var url = 'https://{s}.tiles.mapbox.com/v3/{key}/{z}/{x}/{y}.png';
var attribution = 'MapBox';

var streets   = L.tileLayer(url, {key: "rohs.hkme15d0", attribution: attribution});
var terrain  = L.tileLayer(url, {key: "rohs.hkmf3lfh",   attribution: attribution});

var map = L.map('map', {
    center: new L.LatLng(39.7308819,-105.0348376),
    zoom: 9,
    layers: [streets, cities]
});

var baseMaps = {
	"Streets" : streets,
	"Terrain" : terrain
};

var overlayMaps = {
	"Cities": cities
};

L.control.layers(baseMaps, overlayMaps).addTo(map);

GEOJSON

Programmatically defining map elements is verbose.

GeoJSON is a standard format.

Using GEOJSON

Attach styles to geoJSON shapes:

var myStyle = {
    "color": "red",
    "weight": 5,
    "opacity": 0.65
};

L.geoJson(myLines, { 
        style: myStyle
    }).addTo(map);

Points are converted to markers.

Alternatively you can turn them into a shape.

 var geojsonMarkerOptions = {
    radius: 8,
    fillColor: "#ff7800",
    color: "#000",
    weight: 1,
    opacity: 1,
    fillOpacity: 0.8
};

L.geoJson(someGeojsonFeature, {
    pointToLayer: function (feature, latlng) {
        return L.circleMarker(latlng, geojsonMarkerOptions);
    }
}).addTo(map);

You can attach popups to geoJSON features.

 function onEachFeature(feature, layer) {
    if (feature.properties && feature.properties.popupContent) {
        layer.bindPopup(feature.properties.popupContent);
    }
}

L.geoJson(geojsonFeature, {
    onEachFeature: onEachFeature
}).addTo(map);

You can filter geoJSON datasets.

L.geoJson(someFeatures, {
    filter: function(feature, layer) {
        return feature.properties.show_on_map;
    }
}).addTo(map);

Making geojson

MapBox TileMill - native app

Online editor at http://geojson.io/

MongoDB can serve and query geoJSON

routes

MapQuest routing plugin

 var map = L.map('map', {
    layers: MQ.mapLayer(),
    center: [ 38.895345, -77.030101 ],
    zoom: 15
});
 
var dir = MQ.routing.directions();
 
dir.route({
    locations: [
        '1600 pennsylvania ave, washington dc',
        '935 pennsylvania ave, washington dc'
    ]
});
 
map.addLayer(MQ.routing.routeLayer({ directions: dir, fitBounds: true }));