We count lights, because the night counts

Satellite images of the Earth at night are taken after midnight, when most people are sleeping. They therefore do not provide a correct picture of light use in the early evening. Our group of citizen scientists and researchers has previously developed an app to count light sources along street segments – from illuminated windows and advertising signs to street lamps and traffic lights. As a part of Science Year 2023 – Our Universe, we have modified our app to address this question, and we invited you to count lights again this fall! A twist this year is that in addition to larger local campaigns (>3 participants), it was possible to take part by surveying a single street!

Time for the Night

The campaign for 2023 is over!

We have been counting lights over the last few months, and now the next steps are starting. We are starting to analyze the collected data and will let you know as soon as we have the first results!

The information on the website will remain available for interested parties. You are also welcome to continue using the app for your own use, but the newly collected data will no longer be included in the analysis.

Thank you for your support in counting the lights for this year’s campaign!

Starting from September 1 and going until November 14, you were invited to create a record of lighting change using the Nightlights App. For our special “Time for the Night” campaign this year, we want to find out how the distribution and use of lights changes during the course of the evening and night. For example, how many businesses turn off their signs late at night, and does this depend on how big a city is? To do this, we need people to survey streets at least twice, with at least an hour between the two surveys. It’s easy to do so with the Nightlights app, whether you select an existing street segment or create a new one yourself. The more streets you survey, and the more often you survey them, the better we will understand the times and kinds of lights that turn off.

How to participate

What to count?

We aim to document all artificial light sources that are visible from publicly accessible spaces, from bright floodlights to dim doorbells. Using the Nightlights App, you can systematically count light sources, and document their type, color, emission direction, size, and brightness. Data are collected along street segments, called transects, that typically run from one street corner to another.

Where to count?

You can count anywhere you like! We are interested in city centers, suburban areas, commercial and industrial areas. If there is no transect defined for the street you want to count, you can create transects on your PC or on your phone. We provide step-by-step instructions below on how to create transects, and when to make your observations.

How to count? Follow these 5 steps

Step 1: Set up
  • Complete the Online Tutorial so that you will know everything you need to know about the different types of lights, and how to count them using the app.
  • Install the Nightlights App on your phone, and make sure the app works on your phone and that your location is found when you click the “location button”.
  • If you have problems with these steps, please check our answers to “frequently asked questions”. If you need further help, contact us directly.
  • You can also test the app without an account, by enabling “practice mode” under the “Account” settings. However, any data submitted in practice mode will not be evaluated.
  • If you live outside of the EU: Make sure that data collection and publishing is legal in your country, and that it is legal for you to send your data to servers in the European Union.
  • If you want to get more information, look at our Webinar.
Step 2: Make a plan for the streets you will walk and count
  • In the app, you can see whether any transects are located near to where you live. If there are, you can make an observation on those streets.
  • If you want to do a measurement where there is not yet a transect defined, you can create a transect on your PC or on your phone.
  • Take a look at the existing transects in other cities before you make some yourself. They should generally go from one street corner to the next, and should not be too long.
  • IMPORTANT: To protect the privacy of individuals, we have a rule that transects must contain either zero or at least four households. Transects should generally go from one street corner to the next, but you may need to sometimes do something different (e.g. combine two streets into one transect) to ensure that you don’t have 1-3 households along your transect.
Step 3: Go out at night and count lights
  • You can start counting as soon as it gets dark (after the end of civil twilight, or about an hour after sunset).
  • Check out the instructions here.
Step 4: Check your data
  • After submitting your observation, your data should now be shown within the app. It can also be viewed on your PC.
  • In case you realize that you missed a light source or made another counting error, you will have 10 minutes after submitting the data to edit the survey.
  • If you realize that there is a major error with your survey (e.g., counted along the wrong street), then go to “My surveys” and click “Mark as incorrect”. If you click this button by accident, it can be undone.
  • IMPORTANT: In case you have forgotten one or some lights, please DO NOT create a new survey in which you only record the forgotten light(s). This causes major problems for our analysis, because we consider each survey to be a full count of all of the lights on the street. If the error is small compared to the total number of lights on the transect, it will not cause a large problem – even our most experienced counters miss lights and make mistakes on occasion.
Step 5: Go out and count again
  • For this year’s “Time for the Night” campaign, we want to find out how the lights that are on change during the course of the evening and night. Therefore, we need you to survey your transect(s) at least twice, with at least an hour between the surveys. Three (or more) surveys are also welcome, as are longer time periods between surveys!
  • IMPORTANT: Make sure to select an existing transect when resurveying a transect!
  • Ideally, we want you to survey the same transect(s) twice or more often on the same evening. If this is not feasible, you can do an early and late survey on different evenings.
  • Late surveys (near to or after midnight) are especially interesting. But don’t worry if you don’t want to go out so late – as long as you have at least an hour between your surveys, you are providing useful data.
  • In the app, you can turn on overlays to visualize already surveyed (yellow lines) and unsurveyed transects (blue lines). In the overlays settings, you can also select the time of night.
  • Here are three examples of how a participant might choose to organize their counting on one night. Please feel free to adapt this so that the and surveys fit your schedule. Also note that towards the end of the campaign, it will be dark earlier, so you can start earlier.

The previous Nightlights campaigns - in Germany and worldwide

From the end of August 2021 until mid-November 2021, more than 200 citizen scientists counted and classified almost a quarter of a million artificial light sources in public streets and squares. While counting lights, they have walked 645 kilometers and covered a total of 22 square km in different field sites in Germany and worldwide.

The data was collected in many German cities and communities, notably in Achtenwehr, Berlin, Bochum, Borkheide, Dresden, Erlangen, Erfurt, Freising, Fulda, Herzogenaurach, Köln, Leipzig, Leverkusen, Potsdam, Preußisch-Oldendorf, Rosenheim, Trier, Wittenberg, Würzburg, as well as places outside Germany, including Canada, France, Indonesia, Italy, Ireland, Kenya, Serbia, Spain, Turkey and the USA.

The project participants are now involved in the evaluation and interpretation of the first data and in the work on scientific publications.

The Nightlights team meets regularly online. If you want to stay up to date about our activities, subscribe to our mailing list or register in the Nightlights App to count lights on your own. To help you get started, here is a short app introduction (video). If you have questions about using the app, our answers to “frequently asked questions” will usually help.

Contact us if you want to help organize a local campaign: nachtlichter@gfz-potsdam.de

Thanks for your interest in our project!

Christopher Kyba and the Nachtlichter Co-Design Team