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Cities at Night

The story of one man's fight against light pollution from space.

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Cities at Night is a research project that aims to monitor light emitted by major cities around the world and to raise awareness of light pollution.

It is led by Alejandro Sánchez de Miguel of Complutense University of Madrid, in collaboration with Sherbrooke CEGEP, NASA, the European Space Agency and the Canadian Space Agency, as well as various other institutions and collectives.


Scifabric developed a customised crowdsourced project for Cities at Night on Crowdcrafting, the PyBossa-powered micro-tasking platform.

The project provided researchers with a tool to upload data into the Crowdcrafting platform and ask volunteers to complete a series of tasks to help interpret it. This allowed the team to efficiently analyse a huge data set.


Cities at Night asks volunteers to georeference photographs of cities taken by astronauts aboard the International Space Station.

NASA holds over 1.2 million high resolution, colour photographs taken from the ISS. Researchers aim to assign real-world coordinates to images of cities at night in order to assess levels of light pollution.

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Cities at Night consists of three projects, each with a unique but related purpose...

Scifabric created Dark Skies, the first Cities at Night project, and advised on the development of the follow-up projects Lost at Night and Night Cities ISS. Each project has a neat tutorial providing a step-by-step guide on how volunteers may complete tasks – no prior experience necessary. SciFabric provides full time support and maintenance of all three projects.


Dark Skies: Contributors identify what may be observed in each image, whether stars, a city, an astronaut or simply darkness.

And counting

This project solves a classic image pattern recognition problem, where the volunteers identify objects that algorithms cannot. Identifying stars, cities at night and auroras borealis is complex for computers but people can do it at a glance. The prototype of this project was created in under an hour, proving how straight forward Crowdcrafting is to use.


Lost at Night: Volunteers identify particular cities in the photographs.

And counting

On recognising a particular city in an image – perhaps by its shape, notable features or using local knowledge – contributors record the city's location on a world map. This illustrates how PyBossa software may be used for geolocation.


Night Cities ISS: Photographs of cities at night are accurately georeferenced, that is associated with real world coordinates.

And counting

Volunteers help to match city features in the photograph with the same features shown on a web-based map. The longitude and latitude of each features is recorded. Advanced web-mapping techniques, such as superimposing images on web-based maps and image rotation, are used to facilitate accurate georeferencing of the image.

Ignition & Liftoff

The project has so far attracted more than
30,000 unique contributors
on all three projects. Thanks to users more than
145,000 images have now been classified,
located and georeferenced.

Georeferenced images are used to measure, monitor, compare and contrast light emitted by cities. This information may be fed to governments to encourage reductions in light pollution.

Alejandro Sánchez Photo
The Astronaut

Alejandro Sánchez de Miguel
Researcher at Universidad Complutense de Madrid

"Our experience with the Crowdcrafting platform has been overwhelmingly positive.

It has allowed us to launch several citizen science projects with very few resources and little effort. The platform is flexible enough to use templates or create custom applications. It was a solution that allowed us to only worry about science and no other technical or non scientific issues.

In addition, the team has always been involved and available to give advice and maintain uninterrupted service."