Windshaft-cartodb/docs/anonymous_maps.md

Anonymous Maps

Anonymous Maps allows you to instantiate a map given SQL and CartoCSS. It also allows you to add interaction capabilities using UTF Grid.

Instantiate

Definition

POST /api/v1/map

Params

{
  "version": "1.3.0",
  "layers": [{
    "type": "mapnik",
    "options": {
      "cartocss_version": "2.1.1",
      "cartocss": "#layer { polygon-fill: #FFF; }",
      "sql": "select * from european_countries_e",
      "interactivity": ["cartodb_id", "iso3"]
    }
  }]
}

See MapConfig File Formats for details.

Response

The response includes:

Attributes	Description
layergroupid	The ID for that map, used to compose the URL for the tiles. The final URL is: https://{username}.carto.com/api/v1/map/{layergroupid}/{z}/{x}/{y}.png
updated_at	The ISO date of the last time the data involved in the query was updated.
metadata	Includes information about the layers.
cdn_url	URLs to fetch the data using the best CDN for your zone.

Example

Call

curl 'https://{username}.carto.com/api/v1/map' -H 'Content-Type: application/json' -d @mapconfig.json

Response

{
  "layergroupid": "c01a54877c62831bb51720263f91fb33:0",
  "last_updated": "1970-01-01T00:00:00.000Z",
  "metadata": {
    "layers": [
      {
        "type": "mapnik",
        "meta": {}
      }
    ]
  },
  "cdn_url": {
    "http": "http://cdb.com",
    "https": "https://cdb.com"
  }
}

Map Tile Rendering

Map tiles create the graphical representation of your map in a web browser. The performance rendering of map tiles is dependent on the type of geospatial data model (raster or vector) that you are using.

• Raster: Generates map tiles based on a grid of pixels to represent your data. Each cell is a fixed size and contains values for particular map features. On the server-side, each request queries a dataset to retrieve data for each map tile. The grid size of map tiles can often lead to graphic quality issues.

• Vector: Generates map tiles based on pre-defined coordinates to represent your data, similar to how basemap image tiles are rendered. On the client-side, map tiles represent real-world geometries of a map. Depending on the coordinates, vertices are used to connect the data and display points, lines, or polygons for the map tiles.

Retrieve resources from the layergroup

When you have a layergroup, there are several resources for retrieving layergoup details such as, accessing Mapnik tiles, getting individual layers, accessing defined Attributes, and blending and layer selection.

Mapnik tiles

These raster tiles retrieve just the Mapnik layers. See individual layers for details about how to retrieve other layers.

https://{username}.carto.com/api/v1/map/{layergroupid}/{z}/{x}/{y}.png

Mapbox Vector Tiles (MVT)

Mapbox Vector Tiles (MVT) are map tiles that store geographic vector data on the client-side. Browser performance is fast since you can pan and zoom without having to query the server.

CARTO uses a Web Graphics Library (WebGL) to process MVT files. This is useful since WebGL's are compatible with most web browsers, include support for multiple client-side mapping engines, and do not require additional information from the server; which makes it more efficient for rendering map tiles. However, you can use any implementation tool for processing MVT files.

The following examples describe how to fetch MVT tiles with a cURL request.

MVT and Windshaft

CARTO uses Windshaft as the map tiler library to render multilayer maps with the Maps API. You can use Windshaft to request MVT using the same layer type that is used for requesting raster tiles (Mapnik layer). Simply change the file format .mvt in the URL.

https://{username}.cartodb.com/api/v1/map/HASH/:layer/{z}/{x}/{y}.mvt

The following example instantiates an anonymous map with layer options:

{
  user_name: 'mycartodbuser',
  sublayers: [{
    sql: "SELECT * FROM table_name";
    cartocss: '#layer { marker-fill: #F0F0F0; }'
  }],
  maps_api_template: 'https://{user}.cartodb.com' // Optional
}

Note: If no layer type is specified, Mapnik tiles are used by default. To access MVT tiles, specify https://{username}.cartodb.com/api/v1/map/HASH/{z}/{x}/{y}.mvt as the maps_api_template variable.

Tip: If you are using Named Maps to instantiate a layer, indicate the MVT file format and layer in the response:

https://{username}.cartodb.com/api/v1/map/named/:templateId/:layer/{z}/{x}/{y}.mvt

For all layers in a Named Map, you must indicate Mapnik as the layer filter:

https://{username}.cartodb.com/api/v1/map/named/:templateId/mapnik/{z}/{x}/{y}.mvt

Layergroup Filter for MVT Tiles

To filter layers using Windshaft, use the following request where layers are numbered:

https://{username}.cartodb.com/api/v1/map/HASH/0,1,2/{z}/{x}/{y}.mvt

To request all layers, remove the layergroup filter parameter:

https://{username}.cartodb.com/api/v1/map/HASH/{z}/{x}/{y}.mvt

To filter a specific layer:

https://{username}.cartodb.com/api/v1/map/HASH/2/{z}/{x}/{y}.mvt

Example 1: MVT Tiles with Windshaft, CARTO.js, and MapboxGL

1. Import the required libraries:

<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.9.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.9.0/mapbox-gl.css' rel='stylesheet' />
<script src="http://libs.cartocdn.com/cartodb.js/v3/3.15/cartodb.core.js"></script>

2. Configure Map Client:

mapboxgl.accessToken = '{yourMapboxToken}';

3. Create Map Object (Mapbox):

var map = new mapboxgl.Map({
container: 'map',
zoom: 1,
minZoom: 0,
maxZoom: 18,
center: [30, 0]
});

4. Define Layer Options (CARTO):

var layerOptions = {
user_name: "{username}",
sublayers: [{
sql: "SELECT * FROM {table_name}",
cartocss: "...",
     }]
};

5. Request Tiles (from CARTO) and Set to Map Object (Mapbox):

Note: By default, CARTO core functions retrieve URLs for fully rendered tiles. You must replace the default format (.png) with the MVT format (.mvt).

cartodb.Tiles.getTiles(layerOptions, function(result, err) {
var tiles = result.tiles.map(function(tileUrl) {
return tileUrl
.replace('{s}', 'a')
.replace(/\.png/, '.mvt');
});
map.setStyle(simpleStyle(tiles));
});

Example 2: MVT Libraries with Windshaft and MapboxGL

When you are not including CARTO.js to implement MVT tiles, you must use the map.setStyle parameter to specify vector map rendering.

1. Import the required libraries:

<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.9.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.9.0/mapbox-gl.css' rel='stylesheet'/>

2. Configure Map Client:

mapboxgl.accessToken = '{yourMapboxToken}';

3. Create Map Object (Mapbox):

var map = new mapboxgl.Map({
container: 'map',
zoom: 1,
minZoom: 0,
maxZoom: 18,
center: [30, 0]
});

4. Set the Style

map.setStyle({
    "version": 7,
    "glyphs": "...",
    "constants": {...}, 
    "sources": {
      "cartodb": {
        "type": "vector",
        "tiles": [ "http://{username}.cartodb.com/api/v1/map/named/templateId/mapnik/{z}/{x}/{y}.mvt"
        ],
        "maxzoom": 18
      }
    },
    "layers": [{...}]
});

Tip: If you are using MapboxGL, see the following resource for additional information.

• MapboxGL API Reference
• MapboxGL Style Specifications
• Example of MapboxGL Implementation

Individual layers

The MapConfig specification holds the layers definition in a 0-based index. Layers can be requested individually, in different formats, depending on the layer type.

Individual layers can be accessed using that 0-based index. For UTF grid tiles:

https://{username}.carto.com/api/v1/map/{layergroupid}/{layer}/{z}/{x}/{y}.grid.json

In this case, layer as 0 returns the UTF grid tiles/attributes for layer 0, the only layer in the example MapConfig.

If the MapConfig had a Torque layer at index 1 it could be possible to request it with:

https://{username}.carto.com/api/v1/map/{layergroupid}/1/{z}/{x}/{y}.torque.json

Attributes defined in attributes section

https://{username}.carto.com/api/v1/map/{layergroupid}/{layer}/attributes/{feature_id}

Which returns JSON with the attributes defined, such as:

{ "c": 1, "d": 2 }

Blending and layer selection

https://{username}.carto.com/api/v1/map/{layergroupid}/{layer_filter}/{z}/{x}/{y}.png

Note: currently format is limited to png.

layer_filter can be used to select some layers to be rendered together. layer_filter supports two formats:

• all alias

Using all as layer_filter will blend all layers in the layergroup

https://{username}.carto.com/api/v1/map/{layergroupid}/all/{z}/{x}/{y}.png

• Filter by layer index

A list of comma separated layer indexes can be used to just render a subset of layers. For example 0,3,4 will filter and blend layers with indexes 0, 3, and 4.

https://{username}.carto.com/api/v1/map/{layergroupid}/0,3,4/{z}/{x}/{y}.png

Some notes about filtering:

• Invalid index values or out of bounds indexes will end in Invalid layer filtering errors.
• Ordering is not considered. So right now filtering layers 0,3,4 is the very same thing as filtering 3,4,0. As this may change in the future, it is recommended to always select the layers in ascending order so that you will always get consistent behavior.

Create JSONP

The JSONP endpoint is provided in order to allow web browsers access which don't support CORS.

Definition

GET /api/v1/map?callback=method

Params

Param	Description
config	Encoded JSON with the params for creating Named Maps (the variables defined in the template).
lmza	This attribute contains the same as config but LZMA compressed. It cannot be used at the same time as config.
callback	JSON callback name.

Example

Call

curl "https://{username}.carto.com/api/v1/map?callback=callback&config=%7B%22version%22%3A%221.0.1%22%2C%22layers%22%3A%5B%7B%22type%22%3A%22cartodb%22%2C%22options%22%3A%7B%22sql%22%3A%22select+%2A+from+european_countries_e%22%2C%22cartocss%22%3A%22%23european_countries_e%7B+polygon-fill%3A+%23FF6600%3B+%7D%22%2C%22cartocss_version%22%3A%222.3.0%22%2C%22interactivity%22%3A%5B%22cartodb_id%22%5D%7D%7D%5D%7D"

Response

callback({
  layergroupid: "d9034c133262dfb90285cea26c5c7ad7:0",
  cdn_url: {
    "http": "http://cdb.com",
    "https": "https://cdb.com"
  },
  last_updated: "1970-01-01T00:00:00.000Z"
})

Remove

Anonymous Maps cannot be removed by an API call. They will expire after about five minutes, or sometimes longer. If an Anonymous Map expires and tiles are requested from it, an error will be raised. This could happen if a user leaves a map open and after time, returns to the map and attempts to interact with it in a way that requires new tiles (e.g. zoom). The client will need to go through the steps of creating the map again to fix the problem.