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map_layer

Usage

map_layer: company_regions {
  feature_key: "ISO_A3"
  file: "/map_folder/regions.json"
  format: topojson
  label: "desired label for chart visualization"
  max_zoom_level: 12
  min_zoom_level: 2
  projection: airy
  property_key: "ISO_A3"
  property_label_key: "NAME"
}

Hierarchy

Model File

map_layer

Default Value

None

Accepts

An identifier for your map layer, plus subparameters defining your map layer properties.

Definition

The map_layer parameter lets you define a custom map layer that can then be used to plot regional data, such as counties or zip codes, in Looker and create map charts.

When a map layer exists, typically the interactive map visualization is chosen as the default map visualization. The one exception is the US States map, where Looker uses the Static Map Region chart by default because it uses insets for Alaska and Hawaii.

Map layers can accept TopoJSON or GeoJSON files.

For more information about creating a custom map layer file, see the Creating custom map regions Best Practices page.

Looker recommends that you keep custom map layer files smaller than 5 MB to avoid overwhelming the user's browser tab.

Built-in map layers

Looker includes several built-in map layers. Before creating your own map layers, check whether you can use one of the built-in map layers:

The countries and us_states built-in map layers use proper capitalization for the names of countries and states. Data is plotted to the map layer in a case-sensitive fashion, so your data must also use proper capitalization in order to use these built-in map layers. For example, if your dataset uses lower case "new delhi," the data would not correctly plot on the built-in map layers, which use "New Delhi."

countries — Accepts full country names, ISO 3166-1 alpha-3 three-letter country codes, or ISO 3166-1 alpha-2 two-letter country codes. Note that you must use only one of these three options in your dataset; you cannot use a mix of these options.

If your data uses ISO 3166-1 alpha-2, include the map_layer_name parameter in the definition for your country dimension to ensure that Looker recognizes your data as country codes and does not incorrectly interpret the data as state codes. For example:

  dimension: country {
      type: string
      map_layer_name: countries
      sql: ${TABLE}.country ;;
  }

uk_postcode_areas — Accepts UK postcode areas (for example, L for Liverpool, RH for Redhill, or EH for Edinburgh).
us_states — Accepts full state names and two-letter state abbreviations.
us_counties_fips — Works on string fields that are five-character FIPS county codes for a US county. This layer works only on the interactive map.
us_zipcode_tabulation_areas — Works on string fields that are five-character US zip codes. Dimensions of type: zipcode automatically use the us_zipcode_tabulation_areas map layer.

Zip code regions are based on the 2010 zip code tabulation areas (ZCTAs), so this map layer does not include many zip codes, such as those assigned to P.O. boxes, that do not map directly to regions.

Specifying a map layer

The location of the map can be specified using either the name of a file or a URL.

When using a GeoJSON file, you only need to reference the file subparameter. The general syntax for adding a GeoJSON map layer is:

map_layer: identifier {
  file: "/file_path/file_name.geojson"
}

The general syntax for adding a TopoJSON map layer is:

map_layer: identifier {
  extents_json_url: "string"
  feature_key: "string"
  file: "/file_path/file_name.json" # or use the url subparameter
  format: topojson | vector_tile_region
  label: "string"
  max_zoom_level: number
  min_zoom_level: number
  projection: airy  # or one of many other choices
  property_key: "string"
  property_label_key: "string"
  url: "string" # or use the file subparameter
}

Where:

Parameter	Type	Description
`identifier`	String	Name of the map as you will refer to it in LookML.
`file`	String	Location of the map, specified by the name of a JSON file from your LookML project. The file must be in TopoJSON or GeoJSON format and have a `.json`, `.geojson`, or `.topojson` file extension. You must use the full file path for the JSON file, such as `"/maps/countryobjects.json"` for a file in the `/maps/` directory. If the JSON file is in the root directory and not in a folder, you can indicate the root directory with a single forward slash, like this: `"/countryobjects.json"` If your project is not enabled for folders, Looker displays JSON files in the Data section of the LookML IDE's file list. See the Examples section later on this page for the LookML for each of these scenarios.
`extents_json_url`	String	The URL to a JSON file that defines the geographic extents of each region available in the map layer. This data is used to automatically center the map on the available data for visualization purposes. The JSON file must be a JSON object where the keys are the mapping value of the feature (as specified by `property_key`) and the values are arrays of four numbers representing the west longitude, south latitude, east longitude, and north latitude extents of the region. The object must include a key for every possible value of `property_key`. For example, `extents_json_url: "https://mycompany.com/mapserver/json-extent.js"`. If using this parameter, you must specify your map location using the `url` parameter.
`feature_key`	String	Name of the TopoJSON object that the map layer references. If not specified, the first object will be used.
`format`	Keyword `topojson` or `vector_tile_region`	Data format of the region information. Typically people use `topojson`.
`label`	String	Displayed in the chart configuration UI.
`max_zoom_level`	Number	Maximum zoom level for zooming in the map layer, for visualizations that support zooming.
`min_zoom_level`	Number	Minimum zoom level for zooming in the map layer, for visualizations that support zooming.
`projection`	Keyword	Preferred geographic projection of the map layer when displayed in a visualization that supports multiple geographic projections. The LookML editor lists the many available projections when you add a projection parameter.
`property_key`	String	Property from the TopoJSON data to plot against. TopoJSON supports arbitrary metadata for each region. By default, the first matching property is used. If there's a particular metadata property you want to plot against, specify it here.
`property_label_key`	String	Property from the TopoJSON data to use to label the region. This is useful when the mapping value (defined by `property_key`) is not very human-readable.
`url`	String	Location of the map, specified by a URL that contains your map file.

Examples

When possible, add your map file into your project and then use the file parameter to point to the map file.

You must use the full file path for the JSON file. If your project is not enabled for folders, Looker displays JSON files in the Data section of the LookML IDE's file list.

For example, if your project is enabled for folders and you have a custom map of neighborhoods called my_neighborhoods.json in a directory called maps, you would use the full file path like this:

map_layer: neighborhoods {
  file: "/maps/my_neighborhoods.json"
}

If your project doesn't use folders, uploaded map files are displayed in the project's Data section. In this case, you can just provide the name of the my_neighborhoods.json file:

map_layer: neighborhoods {
  file: "my_neighborhoods.json"
}

Alternatively, you could specify that a custom neighborhoods map is hosted elsewhere, such as at https://wherever.com/my_neighborhoods.json:

map_layer: neighborhoods {
  url: "https://wherever.com/my_neighborhoods.json"
}

After the map layer is defined (by specifying a file or using the url parameter) you can specify that a dimension's values should be associated with a geographic region on your custom map. In the dimension, use the map_layer_name parameter to specify the name you used in the map_layer parameter.

dimension: neighborhood {
  type: string
  map_layer_name: neighborhoods    # this is your map layer
  sql: ${TABLE}.neighborhood_code
}

When you query this dimension and open the visualization section, Looker charts the data using the neighborhoods JSON file, as defined in the map_layer parameter in your model file.

Things to know

Static map (regions) charts

Setting Map to Auto in Static Map (Regions) charts relies on having map_layer specified in the LookML model specifying a map layer. Without that parameter set, users get an error if they select Auto but can still use Looker's built-in maps.

GeoJSON files

Similar to TopoJSON files, GeoJSON files can have either the .geojson or the .json file extension but must contain geographic data in GeoJSON format. When using a GeoJSON file, you only need to reference the file subparameter.

Using `map_layer` with IDE folders

If you have IDE folders enabled for your project, you need to use the file path when you specify a project file for map_layer:

map_layer: neighborhoods {
  file: "/maps/my_neighborhoods.json"
}