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Screenshot from DuckDB Spatial example


Bases: BaseArrowLayer

The HeatmapLayer visualizes the spatial distribution of data.


From GeoPandas:

import geopandas as gpd
from lonboard import Map, HeatmapLayer

# A GeoDataFrame with Point geometries
gdf = gpd.GeoDataFrame()
layer = HeatmapLayer.from_geopandas(gdf)
m = Map(layer)

From geoarrow-rust:

from geoarrow.rust.core import read_parquet
from lonboard import Map, HeatmapLayer

# Example: A GeoParquet file with Point geometries
table = read_parquet("path/to/file.parquet")
layer = HeatmapLayer(
    get_fill_color=[255, 0, 0],
m = Map(layer)

aggregation class-attribute instance-attribute

aggregation = tag(sync=True)

Defines the type of aggregation operation

Valid values are 'SUM', 'MEAN'.

  • Type: str, optional
  • Default: "SUM"

auto_highlight class-attribute instance-attribute

auto_highlight = tag(sync=True)

When true, the current object pointed to by the mouse pointer (when hovered over) is highlighted with highlightColor.

Requires pickable to be True.

  • Type: bool
  • Default: False

debounce_timeout class-attribute instance-attribute

debounce_timeout = tag(sync=True)

Interval in milliseconds during which changes to the viewport don't trigger aggregation.

  • Type: int, optional
  • Default: 500

extensions class-attribute instance-attribute

extensions = tag(sync=True, **widget_serialization)

A list of layer extension objects to add additional features to a layer.

get_weight class-attribute instance-attribute

get_weight = FloatAccessor(None, allow_none=True)

The weight of each object.

  • Type: FloatAccessor, optional
    • If a number is provided, it is used as the weight for all objects.
    • If an array is provided, each value in the array will be used as the weight for the object at the same row index.
  • Default: 1.

intensity class-attribute instance-attribute

intensity = tag(sync=True)

Value that is multiplied with the total weight at a pixel to obtain the final weight.

  • Type: float, optional
  • Default: 1

opacity class-attribute instance-attribute

opacity = tag(sync=True)

The opacity of the layer.

  • Type: float. Must range between 0 and 1.
  • Default: 1

pickable class-attribute instance-attribute

pickable = tag(sync=True)

Whether the layer responds to mouse pointer picking events.

This must be set to True for tooltips and other interactive elements to be available. This can also be used to only allow picking on specific layers within a map instance.

Note that picking has some performance overhead in rendering. To get the absolute best rendering performance with large data (at the cost of removing interactivity), set this to False.

  • Type: bool
  • Default: True

radius_pixels class-attribute instance-attribute

radius_pixels = tag(sync=True)

Radius of the circle in pixels, to which the weight of an object is distributed.

  • Type: float, optional
  • Default: 30

selected_index class-attribute instance-attribute

selected_index = tag(sync=True)

The positional index of the most-recently clicked on row of data.

You can use this to access the full row of data from a GeoDataFrame


Setting a value here from Python will do nothing. This attribute only exists to be updated from JavaScript on a map click. Note that pickable must be True (the default) on this layer for the JavaScript onClick handler to work; if pickable is set to False, selected_index will never update.

Note that you can use observe to call a function whenever a new value is received from JavaScript. Refer here for an example.

table class-attribute instance-attribute

table = PyarrowTableTrait(allowed_geometry_types={POINT})

A GeoArrow table with a Point column.

This is the fastest way to plot data from an existing GeoArrow source, such as geoarrow-rust or geoarrow-pyarrow.

If you have a GeoPandas GeoDataFrame, use from_geopandas instead.

threshold class-attribute instance-attribute

threshold = tag(sync=True)

Ratio of the fading weight to the max weight, between 0 and 1.

For example, 0.1 affects all pixels with weight under 10% of the max.

Ignored when color_domain is specified.

  • Type: float, optional
  • Default: 0.05

visible class-attribute instance-attribute

visible = tag(sync=True)

Whether the layer is visible.

Under most circumstances, using the visible attribute to control the visibility of layers is recommended over removing/adding the layer from the Map.layers list.

In particular, toggling the visible attribute will persist the layer on the JavaScript side, while removing/adding the layer from the Map.layers list will re-download and re-render from scratch.

  • Type: bool
  • Default: True

weights_texture_size class-attribute instance-attribute

weights_texture_size = tag(sync=True)

Specifies the size of weight texture.

  • Type: int, optional
  • Default: 2048

from_duckdb classmethod

    sql: Union[str, DuckDBPyRelation],
    con: Optional[DuckDBPyConnection] = None,
    crs: Optional[Union[str, CRS]] = None,
    **kwargs: Unpack[HeatmapLayerKwargs]
) -> Self

Construct a Layer from a duckdb-spatial query.

DuckDB Spatial does not currently expose coordinate reference system information, so the user must ensure that data has been reprojected to EPSG:4326 or pass in the existing CRS of the data in the crs keyword parameter.


  • sql (Union[str, DuckDBPyRelation]) –

    The SQL input to visualize. This can either be a string containing a SQL query or the output of the duckdb sql function.

  • con (Optional[DuckDBPyConnection], default: None ) –

    The current DuckDB connection. This is required when passing a str to the sql parameter or when using a non-global DuckDB connection. Defaults to None.

Other Parameters:

  • crs (Optional[Union[str, CRS]]) –

    The CRS of the input data. This can either be a string passed to pyproj.CRS.from_user_input or a pyproj.CRS object. Defaults to None.


  • Self

    A Layer with the initialized data.

from_geopandas classmethod

    gdf: GeoDataFrame,
    auto_downcast: bool = True,
    **kwargs: Unpack[HeatmapLayerKwargs]
) -> Self

Construct a Layer from a geopandas GeoDataFrame.

The GeoDataFrame will be reprojected to EPSG:4326 if it is not already in that coordinate system.


  • gdf (GeoDataFrame) –

    The GeoDataFrame to set on the layer.

Other Parameters:


  • Self

    A Layer with the initialized data.