Layer Management

Layers let you manage multiple data overlays on the map. Each layer wraps a Makie plot object with a name and visibility toggle, and integrates with the built-in layers panel (☰) in the UI.

Adding Layers

Use plot_geometry! or any Makie plotting function on app.map_axis, then register it as a layer with add_layer!:

using GeoExplorer, GeoJSON, GLMakie

app = explore()

# Plot data and register as a layer
geom = GeoJSON.read("boundaries.geojson")
plt = plot_geometry!(app, geom)
add_layer!(app, "Boundaries", plt)

# Or use Makie directly (coordinates in Web Mercator)
scatter_plt = scatter!(app.map_axis, xs, ys; color=:red, markersize=8)
add_layer!(app, "My Points", scatter_plt)

using GeoExplorer, GeoJSON, GLMakie, Extents

fig = Figure(size=(800, 600))
app = explore(extent=Extents.Extent(X=(-105.30, -105.24), Y=(39.98, 40.03)), figure=fig)

# Add a polygon layer
polygon = GeoJSON.read("""
{
  "type": "Polygon",
  "coordinates": [[
    [-105.29, 40.02],
    [-105.27, 40.02],
    [-105.27, 40.00],
    [-105.29, 40.00],
    [-105.29, 40.02]
  ]]
}
""")
plt1 = plot_geometry!(app, polygon; color=(:dodgerblue, 0.3), strokecolor=:dodgerblue, strokewidth=2)
add_layer!(app, "Zone A", plt1)

# Add a scatter layer
points = GeoJSON.read("""
{
  "type": "MultiPoint",
  "coordinates": [
    [-105.275, 40.015],
    [-105.265, 40.005],
    [-105.255, 40.020],
    [-105.285, 40.010],
    [-105.260, 40.012]
  ]
}
""")
plt2 = plot_geometry!(app, points; color=:red, markersize=12)
add_layer!(app, "Stations", plt2)

# Add a line layer
route = GeoJSON.read("""
{
  "type": "LineString",
  "coordinates": [
    [-105.29, 39.99],
    [-105.27, 40.01],
    [-105.25, 40.005],
    [-105.24, 40.02]
  ]
}
""")
plt3 = plot_geometry!(app, route; color=:green, linewidth=3)
add_layer!(app, "Route", plt3)

wait(app.map)
save("layers_example.png", fig)

Map with polygon, scatter, and line layers in Boulder, CO

The Layers Panel

Click the ☰ button in the top-right corner to open the layers panel. From there you can:

• Toggle visibility with the checkbox next to each layer name
• Zoom to a layer’s extent with the zoom button (⌖)

Programmatic Layer Control

# Toggle visibility on/off
toggle_layer!(app, "Stations")

# Get a layer by name
layer = get_layer(app, "Stations")
layer.visible[]  # true or false

# Zoom the map to fit a layer's extent
zoom_to_layer!(app, "Zone A")
zoom_to_layer!(app, "Zone A", padding=0.2)  # 20% padding

# Remove a layer (deletes the plot from the map)
remove_layer!(app, "Route")

The Layer Struct

Field	Type	Description
name	String	Display name shown in the layers panel
plot	Any	Reference to the Makie plot object
visible	Observable{Bool}	Reactive visibility state

Layer Functions

Function	Description
add_layer!(app, name, plot)	Register a plot as a named layer
remove_layer!(app, name)	Remove a layer and delete its plot
toggle_layer!(app, name)	Toggle a layer’s visibility
get_layer(app, name)	Get a Layer by name (or nothing)
zoom_to_layer!(app, name; padding=0.1)	Zoom the map to fit a layer’s extent