4.9 KiB
Getting Started
Although the most straightforward way to use Torque is through either the CARTO Editor, or by passing the layer's viz.json to CARTO.js, many use cases work best with the standalone Torque.js. Assuming you have a public dataset with a date column, it is really simple to create an animated map with the library. First, you need to have a Leaflet map prepared in an HTML page:
<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.css" />
<body>
<div id="map"></div>
<script src="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.js"></script>
<script>
var map = new L.Map('map', {
zoomControl: true,
center: [40, 0],
zoom: 3
});
L.tileLayer('http://{s}.api.cartocdn.com/base-dark/{z}/{x}/{y}.png', {
attribution: 'CARTO'
}).addTo(map);
</script>
</body>
This HTML file automatically generates the Torque.js library, which includes any Torque dependencies. For Torque to work with your table, you only need a username, the name of the table, and a CartoCSS string to style the map. Leaflet's method addTo adds the Torque layer to the map. play runs the animation with the options specified in the CartoCSS properties.
<script>
var CARTOCSS = [
'Map {',
'-torque-time-attribute: "date";',
'-torque-aggregation-function: "count(cartodb_id)";',
'-torque-frame-count: 760;',
'-torque-animation-duration: 15;',
'-torque-resolution: 2',
'}',
'#layer {',
' marker-width: 3;',
' marker-fill-opacity: 0.8;',
' marker-fill: #FEE391; ',
' comp-op: "lighten";',
'}'
].join('\n');
var torqueLayer = new L.TorqueLayer({
user : 'your_username',
table : 'your_table_name',
cartocss: CARTOCSS
});
torqueLayer.addTo(map);
torqueLayer.play()
</script>
You can use any kind of tile source outside CARTO, by specifying the location of a valid TileJSON file:
var torqueLayer = new L.TorqueLayer({
tileJSON: 'http://url.to/tile.json'
cartocss: CARTOCSS
});
Optionally, it is also possible to use a custom SQL query for your visualization:
var torqueLayer = new L.TorqueLayer({
user : 'your_username',
table : 'your_table_name',
sql_query : 'SELECT * FROM your_table_name WHERE whatever'
cartocss: CARTOCSS
});
Like in a video player, you can use animation control methods such as play, stop and pause at any point. Torque's animator fires a change:time event each time the animation "ticks" to the next frame, and there are a number of properties and methods that can be run during playback, which are detailed in the API documentation. At any point, for example, the styling of the layer's markers can be changed using the layer.setCartoCSS('##style##').
Usage Examples
The best way to start learning about the library is by taking a look at some of the examples below:
- A basic example using the WWI British Navy dataset - (view live / source code)
- Using tileJSON to fetch tiles - (view live / source code)
- A car's route at the Nürburgring track mapped in Torque - (view live / source code)
Additional Torque Resources
The following links contain examples, and other public information, about using Torque maps.
- Torque CartoCSS Reference page, useful for building parsers, tests, compilers, and syntax highlighting/checking
- CARTO repository of examples
- A CARTO time example of a Torque map and data
- CARTO wiki page describing how spatial aggregration works
- The Guardian's Data Blog about Royal Navy ships in WWI using a Torque map
- An example of how to create a simple Torque visualization and the source code used to create the example
- An example of how to use CARTO.js to add a Torque layer from a named map with auth_tokens enabled