Fused Map

Fused Map is an experimental feature

Fused Map is hidden by default. To turn it on, go to Preferences → Experimental features → Fused map widget.

Fused Map is a map widget in Fused. It draws geospatial data from a UDF, a SQL query, or a tile URL: points, polygons, H3 hexagons, and raster tiles, with many layers on one map.

Its type is fused-map. It works like any other widget: configure it in JSON, connect UDFs with edges, and share it as a URL. To see working examples, open the Fused Map example canvas. For the props, see the Fused Map API reference.

Add a Fused Map widget

1. In the Workbench canvas, select the Widget icon in the toolbar.
2. In the Widget configuration panel, select Preset, then Maps and geo, then Fused map.
3. Connect the UDF node to the widget node with an edge.
4. In the JSON, set udf to the name of the UDF in double braces, for example {{my_udf}}.

For a faster way, drag an edge from the output handle of a UDF node to an empty spot on the canvas, then select Fused map in the menu. Workbench creates a Fused Map widget that is already connected to the UDF and draws its result.

note

The UDF must be on the same canvas. The name in {{ }} must match the UDF name exactly, with the same case.

Layer types and data sources

Set the type of each layer to geojson, h3, raster, mvt, heatmap, scatterplot, arc, or deck-geojson. Each layer reads its data in one of four ways:

Property	What the map does
udf	Runs the UDF one time and draws the whole result.
udf and tile: true	Runs the UDF for each map tile. The UDF gets the tile bounds.
sql	Runs a DuckDB query on a UDF result, then draws the rows.
tileUrl	Reads tiles from a URL with {z}, {x}, and {y} placeholders.

The UDF returns a GeoDataFrame for geojson layers, a DataFrame with an H3 column for h3 layers, and an image array for raster layers. A DataFrame with latitude and longitude columns also works for geojson layers: set latColumn and lngColumn. Every other column is a property of the feature. The tooltip, the filters, and the data-driven colors use these properties.

If tile is true, the map sends the tile area to the UDF in the bounds argument, as [west, south, east, north] in EPSG:4326. Return only the rows inside bounds.

First argument must be named bounds

For tile: true, the UDF's first argument must be named bounds and typed as fused.types.Bounds, for example:

@fused.udf
def udf(bounds: fused.types.Bounds):
    ...

If the UDF has no bounds argument, every tile gets the same result.

Example

This map shows San Francisco Airbnb listings as points on top of a Bay Area seismic hazard raster.

Show the widget JSON

{
  "type": "fused-map",
  "props": {
    "basemap": "mapbox://styles/mapbox/dark-v11",
    "centerLng": -122.3,
    "centerLat": 37.7,
    "zoom": 9.5,
    "autoFit": false,
    "layers": [
      {
        "id": "seismic",
        "name": "Bay Area seismic hazard (raster)",
        "type": "raster",
        "udf": "{{bay_area_seismic_raster}}",
        "tile": true,
        "minZoom": 0,
        "maxZoom": 19,
        "style": { "opacity": 0.6 }
      },
      {
        "id": "sf_listings",
        "name": "SF Airbnb listings",
        "type": "geojson",
        "udf": "{{sf_listings}}",
        "latColumn": "latitude",
        "lngColumn": "longitude",
        "tooltip": ["name", "price_in_dollar", "room_type"],
        "legend": true,
        "style": {
          "fillColor": { "type": "categorical", "attr": "room_type", "palette": "Bold" },
          "pointRadius": 4,
          "opacity": 0.85
        }
      }
    ]
  }
}

The Fused Map example canvas has working UDF and widget examples. For the style, tooltip, legend, and filter props, see the Fused Map API reference.

The sidebar

The sidebar lets the viewer change the style, the filters, and the SQL of each layer in the browser. Each layer has a Style tab and a Filters tab. In Style, set the layer type, the fill mode (for example By value with a property, a palette, steps, and a domain), the stroke, and the opacity.

These changes are temporary. To keep them, select Save to widget to write them into the widget configuration, or select Copy config and paste the result into the JSON. Select Reset to undo the changes.