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Base layers

Base layers are the basemap that sits underneath all other layers on the map. They are managed separately from regular layer cards because only one base layer can be visible at a time, and they typically have no toggleable visibility, no statistics, and no constraints.

Layer Type selector — Standard / Swipe — and Layout Style at the top of the layer card editor

When to use

Use a base layer for any map background the user picks from a basemap selector — for example:

  • OpenStreetMap, Carto, or Stamen tile sets (XYZ)
  • A WMTS topographic or satellite background
  • A custom organisation basemap served as XYZ or WMS

Use a standard layer card instead when the data should be toggleable, stack with other layers, or carry styling, statistics, or constraints.

Configure

Each base layer has:

  • Name — shown in the basemap picker.
  • Preview image — optional thumbnail (preview URL) shown next to the name in the picker.
  • Data source — usually a single XYZ, WMTS, or WMS source. Multiple sources are allowed but uncommon.
  • Attribution — required text (and optional link) credited on the map.

Layout, statistics, constraints, and most layer-card controls do not apply. The isBaseLayer: true flag at the top of the layer marks it as a basemap rather than a data overlay.

Validation

  • At least one data source is required.
  • Attribution text is required.
  • The first base layer in the list is the default selection on map load.

Add a base layer

  1. Open the Add New Layer screen — click Add Layer at the top of the Layers tab. This is important: when you launch Add Layer from inside an interface group, the second tile becomes Import Layer Card and the Base Layer option is hidden.
  2. Pick the Base Layer tile in the type selector.
  3. Fill in the slim base-layer form:
    • Name — what the basemap picker will show.
    • Preview image URL — optional thumbnail.
    • Data source — provide the URL and pick the format (XYZ, WMTS, or WMS are typical).
    • Attribution — required.
  4. Save Layer. The new base layer appears in the Base Layers section at the top of the Layers tab.
  5. To make a base layer the default selection on map load, drag it to the top of the Base Layers list.