Temporal Map: Comparing Toronto by Day and Night

This interactive map explores the city of Toronto through time contrasting its daytime landscape with its nighttime illumination. Using a temporal swipe interface, the map allows users to slide between daytime satellite imagery (Esri World Imagery) and nighttime Earth observation data (NASA GIBS Black Marble), revealing how urban form and light patterns intertwine across the metropolis.

Data Sources

• Daytime: Esri World Imagery, which is a high-resolution composite of true-color daytime scenes showing roads, parks, and urban density.

• Nighttime: NASA GIBS Black Marble, which is a global night-light imagery derived from the VIIRS sensor aboard the Suomi-NPP satellite, capturing artificial illumination and energy use.

• Boundary Overlay: Toronto’s administrative boundary (Open Data Toronto) helps delineate the urban core and surrounding municipalities.

  
  

Interaction

The map uses a leaflet split-view slider to visually compare spatial patterns:

• Drag the divider left and right to transition between day and night views.

• Zoom in to explore specific neighborhoods — bright downtown cores, dimmer residential zones, and dark natural areas like the Don Valley or Rouge Park.

Insights

By toggling between day and night, several urban dynamics become visible:

• Downtown and waterfront remain the brightest after dark, mirroring daytime density.

• Industrial zones and highways emit strong light signatures, tracing energy and movement.

• Green spaces and ravines,which are prominent in daylight, fade into darkness, highlighting the city’s environmental corridors.

This visualization highlights how satellite data reveal not just spatial layout but temporal character, a city that changes form as sunlight fades and human activity glows.

Why It Matters

Temporal composites like this bridge remote sensing and urban analytics, allowing planners, researchers, and citizens to:

• Identify energy-intensive zones

• Track urban expansion and densification

• Study relationships between light pollution, population, and ecology

The combination of NASA’s global night-lights and high-resolution daytime imagery turns Toronto into a living temporal canvas, bright, complex, and ever-evolving.