An Interactive Map with Leaflet, GeoJSON, and jQuery Using Bootstrap
A Side Project – An Interactive Parking Map of Innsbruck
When I recently moved to Innsbruck, I noticed that there was no interactive map for the parking system available. The amount of time you can park your car depends on the zone your car is located in. There are 20 parking zones and they are defined by their bordering streets in the city. Innsbruck is very dense and parking is always a hot topic. So I thought having an interactive map makes it easier to find zones where you can leave your car longer, also if your are not so familiar with the street names. The city of Innsbruck offers the GIS data at the open data portal of Austria, which made it quite easy to implement such a map. I used the following technologies for creating this map:
- Leaflet.js for rendering the open streetmap data
- jQuery for the interactive elements
- GeoJSON for the data
- Bootstrap for the single page layout
- Disqus for the comment section
The source code is available at my Github account. The implementation is available here and also at the Austrian Open Data Portal.
Code Snippets
Explaining the whole source code would be a bit too much for this post and most of it is pretty self explanatory, but in the following section I would like to highlight a few things of the project.
Initializing
In the top of the HTML file, we load the JavaScript file which contains all the functions and variables for our implementation. The script is called parkraum.js (parkraum means parking space in German).
The initialization of the Javascript code is straight forward with jQuery. I structured the initialization into a few components, as you can see in the following example.
<script>
$(document).ready(function() {
initMap();
placeZonesOnMap();
loadScrolling();
populateParkzoneDropdown();
});
</script>
We first initialize the Map itself, then place the parking zones, initialize the page scrolling to make it more smoothly and then populate the drop down menu with the available parking zones.
Initialize the Map
The first step is the initialization of the map with Leaflet. Note that map is a global variable. The coordinates [47.2685694, 11.3932759] are the center of Innsbruck annd 14 is the zoom level. In order to offer the map on a public page, you need to register with mapbox, a service which provides the tiles for the map. Mapbox is free for 50k map views per month. Make sure to use your own key and show some attribution.
// Initialize map and add a legend
function initMap() {
map = L.map('map').setView([47.2685694, 11.3932759], 14);
tileLayer = L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=YOUR_API_KEY, {
maxZoom: 18,
attribution: 'Map data © <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
'<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
'Imagery © <a href="http://mapbox.com">Mapbox</a>',
id: 'mapbox.light'
}).addTo(map);
addLegend();
}
We also add a legend to the map, for indicating the parking area type with colors. There exist 4 types of parking areas and we just add little squares with that colors to the map. The legend improves the readability of the map.
/* Add a legend to the map. */
function addLegend(){
var legend = L.control({position: 'bottomright'});
legend.onAdd = function (map) {
var div = L.DomUtil.create('div', 'info legend');
div.innerHTML =
'<i style="background:#72B2FF";></i><span style="font-weight: 600;">90 Minuten Kurzparkzone</span><br>' +
'<i style="background:#BEE7FF";></i><span style="font-weight: 600;">180 Minuten Kurzparkzone</span><br>' +
'<i style="background:#A3FF72";></i><span style="font-weight: 600;">Werktags Parkstraße</span><br>' +
'<i style="background:#D8D0F4";></i><span style="font-weight: 600;">Parkstraße</span><br>';
return div;
};
legend.addTo(map);
}
The final map with the legend looks like this:
Reading Data, Adding Layers
I obtained the shapefiles with the geographic information from the Austrian Open Data Portal. The data seems to be exported from ArcGIS and I manually converted it into GeoJSON, which is directly supported by Leaflet.js without any plugins. To do this, I just copied the polygon data into the GeoJSON structure. I also separated the quite large file into smaller junks, each parking zone in one file.
Below you can see an example how the JSON looks like for the parking zone C. The structure contains the short name (“C”), some additional information about the zone, attributes for the color, opacity and outline and of course the actual coordinates, which make up a polygon covering the parking area.
{
"type": "Feature",
"properties": {
"parkzonenKuerzel": "C",
"parkzoneInfo":"Kurzparkzone 90 min gebührenpflichtig, werktags Mo-Fr von 9-21 Uhr und Sa von 9-13 Uhr, ½ Stunde EUR 0.70, 1 Stunde EUR 1.40, 1½ Stunden EUR 2.10.",
"style": {
"weight": 2,
"color": "#999",
"opacity": 1,
"fillColor": "#72B2FF",
"fillOpacity": 0.5
}
},
"geometry":{
"type":"Polygon",
"coordinates":[
[
[11.389460535000069,47.261162269000067],[11.389526044000036,47.261021078000056],
...
]
]
}
}
I created a small object containing the name of a parking zone, the relative path of the JSON file and a place holder for layer information.
var parkzonen = [{
parkzone: 'C',
jsonFile: './data/zoneC.json',
layer: ''
}, {
parkzone: 'D',
jsonFile: './data/zoneD.json',
layer: ''
}
...
}];
This is globally available inside the JS file. The actual loading of the parking zones and the placement of the polygones on the map is happening in the following function. It uses jQuery to load the JSON files. Note that jQuery expects the files to be delivered by a Web server. So in order for this to work, you need to make sure that the files can be served by a Web server , also on your local development machine. You can try this very easy, if you execute the following python statement within the root directory of your local development directory:``` sudo http-server -p 80 .
function placeZonesOnMap() {
for (var zone in parkzonen) {
var parkzonenKuerzel = parkzonen[zone].parkzone;
var jsonURL = parkzonen[zone].jsonFile;
$.ajaxSetup({
beforeSend: function(xhr) {
if (xhr.overrideMimeType) {
xhr.overrideMimeType("application/json");
}
}
});
$.getJSON(jsonURL, function(data) {
placeZoneOnMap(data);
});
}
}
// Place zone on map
function placeZoneOnMap(data) {
var parkzonenKuerzel = data.properties.parkzonenKuerzel;
for (var zone in parkzonen) {
if(parkzonen[zone].parkzone===parkzonenKuerzel){
var layer = addGeoJSONToMap(data);
parkzonen[zone].layer= layer;
}
}
}
function addGeoJSONToMap(data){
var layer = L.geoJson([data], {
style: function(feature) {
return feature.properties && feature.properties.style;
},
onEachFeature: onEachFeature,
}).addTo(map);
return layer;
}
function onEachFeature(feature, layer) {
var popupContent = 'Parkzone: <span style="font-weight: 900; font-size: 150%;">' + feature.properties.parkzonenKuerzel + '</span></br>' + feature.properties.parkzoneInfo;
layer.bindPopup(popupContent);
var label = L.marker(layer.getBounds().getCenter(), {
icon: L.divIcon({
className: 'label',
html: '<span style="font-weight: 900; font-size: 200%;color:black;">' + feature.properties.parkzonenKuerzel+'</span>',
iconSize: [100, 40]
})
}).addTo(map);
}```
The for loop iterates over the object, where we stored all the parking zones, respectively the JSON file locations. We load the files, one by one, and place the polygons on the map. This of course works in an asynchronous fashion. After this step, the polygons become visible on the map. We also add a clickable info box on all parking zones, which then display additional information.
## Dropdown Selection for Marking and Highlighting a Parking Zone
Users are able to select one of the parking zones from a drop down list. In the first step, we add all parking zones by iterating over the parking zones object. Once selected, the parking zone will change the color and therefore be highlighted. To do that, we remove the layer of the parking zone and add it again in a different color.
function populateParkzoneDropdown(){ $('#selectParkzone’).empty(); $('#selectParkzone’).append($(‘</option>').val(‘Bitte Auswählen’).html(‘Zonen’)); $.each(parkzonen, function(i, p) { $('#selectParkzone’).append($(‘</option>').val(p.parkzone).html(p.parkzone)); });
}
$("#selectParkzone”).change(function () { var selectedParkZone = $("#selectParkzone”).val(); changeParkzoneColor(selectedParkZone);
});
function changeParkzoneColor (selectParkzone){ resetMap();
for (var zone in parkzonen) {
if(parkzonen[zone].parkzone==selectParkzone){
var layer = parkzonen[zone].layer;
map.removeLayer(layer);
layer.setStyle({
fillColor: 'red',
fillOpacity: 0.7
});
map.addLayer(layer);
}
}
}
// Reset all layers function resetMap(){ console.log(‘reset’); map.eachLayer(function (layer) { map.removeLayer(layer); }); map.addLayer(tileLayer); placeZonesOnMap(); }
## Show the Current Location
Showing the current location is also a nice feature. By clicking on a button, the map scrolls to the current location, which is transmitted by the browser. Note that this only works if you deliver your pages with HTTPS!
function currentPosition() { if (navigator.geolocation) { navigator.geolocation.getCurrentPosition(function(position) { latit = position.coords.latitude; longit = position.coords.longitude; //console.log(‘Current position: ' + latit + ' ' + longit); //alert(‘Current position: ' + latit + ' ' + longit); // this is just a marker placed in that position var abc = L.marker([position.coords.latitude, position.coords.longitude]).addTo(map); // move the map to have the location in its center map.panTo(new L.LatLng(latit, longit)); }); } }```
Navigation and Scrolling
The single page app utilises bootstrap for rendering the content nicely and providing the navigation features. The following code snippet show how we can make all links scroll smoothly.
// use the first element that is "scrollable"
function scrollableElement(els) {
for (var i = 0, argLength = arguments.length; i < argLength; i++) {
var el = arguments[i],
$scrollElement = $(el);
if ($scrollElement.scrollTop() > 0) {
return el;
} else {
$scrollElement.scrollTop(1);
var isScrollable = $scrollElement.scrollTop() > 0;
$scrollElement.scrollTop(0);
if (isScrollable) {
return el;
}
}
}
return [];
}
// Filter all links
function filterPath(string) {
return string
.replace(/^\//, '')
.replace(/(index|default).[a-zA-Z]{3,4}$/, '')
.replace(/\/$/, '');
}
function loadScrolling() {
var locationPath = filterPath(location.pathname);
var scrollElem = scrollableElement('html', 'body');
$('a[href*=\\#]').each(function() {
var thisPath = filterPath(this.pathname) || locationPath;
if (locationPath == thisPath &&
(location.hostname == this.hostname || !this.hostname) &&
this.hash.replace(/#/, '')) {
var $target = $(this.hash),
target = this.hash;
if (target) {
var targetOffset = $target.offset().top;
$(this).click(function(event) {
event.preventDefault();
$(scrollElem).animate({
scrollTop: targetOffset
}, 400, function() {
location.hash = target;
});
});
}
}
});
}