VIIRS Night Lights over Toronto: Mapping the City’s Nocturnal Energy

Illuminating Toronto from Space

Every night, satellites orbiting hundreds of kilometers above Earth capture a dazzling view of human activity. One of the most remarkable datasets comes from NASA and NOAA’s VIIRS (Visible Infrared Imaging Radiometer Suite) instrument. It records night-time light emissions from streetlights, buildings, vehicles, and even ships giving us a glowing fingerprint of urban life.

This visualization focuses on Toronto, a vibrant city whose energy is as visible from space as it is on the ground. Using data from the VIIRS Day and Night Band (DNB), we can explore where the city shines brightest and where the darkness prevails.

How the Map Was Made

The imagery above was generated using the VIIRS monthly composite of average radiance.

1. Data Source: NASA’s Earth Observation Group (VIIRS DNB, monthly average).

2. Processing:

   • The dataset was clipped to the Toronto administrative boundary.

   • Radiance values were converted to floating-point arrays and normalized between the 2nd and 98th percentiles to decrease the effect of outliers (e.g., unusually bright areas).

   • Negative and NaN values were masked to zero.

   • A Gaussian blur (σ = 2) added a soft glow effect, improving spatial patterns.

     
     

3. Visualization:

   • Rendered with a “magma” colormap for intensity visualization.

   • Overlaid on OpenStreetMap basemaps for geographic context.

What the Patterns Reveal

In the heatmap, the brightest regions correspond to:

• Downtown Toronto – the core of continuous illumination, stretching from the Financial District through Yonge–Dundas Square.

• Pearson International Airport – one of the most consistently bright zones due to runway lighting.

• Major corridors such as the 401, 404, and Gardiner Expressway, visible as luminous linear features.

The darker patches usually mark:

• Parks and ravines such as High Park, Don Valley, and Rouge National Urban Park.

• Water bodies, especially Lake Ontario, which appears almost black.

  
  

These contrasts beautifully trace the city’s built environment, energy distribution, and land use patterns.

Why Night Lights Matter

VIIRS night-time lights are more than a visual appeal, they are a powerful proxy for human presence and activity. Researchers use this data to study:

• Urbanization and population density

• Economic development and energy consumption

• Disaster impacts (e.g., post-storm power outages)

• Light pollution and environmental monitoring

  
  

In Toronto’s case, night-light intensity mirrors urban sprawl and transportation infrastructure, providing a quantitative lens on how the city grows and glows.

A Glimpse into the Future

Combining VIIRS data with temporal analysis say, from 2012 to 2025 could show how Toronto’s luminosity has evolved with population growth, infrastructure projects, and sustainability efforts. By pairing night lights with other datasets such as energy grids or traffic networks, we can better understand urban metabolism and environmental impact.

Explore It Yourself

The data and visualization code were built in Python using geemap, rasterio, and matplotlib. You can reproduce or adapt this workflow for any city on Earth, just change the region and let the lights guide your analysis.

“Cities never sleep, and from space, their stories are written in light.”