Tuesday, March 24, 2020

Street view with the lights out

Ken Walczak from the Adler Planetarium in Chicago recently sent me a set of two cool photos I want to share. Here's what he had to say about them:

I got home after an evening event and didn't realize at first why there was such a different quality to the ambience of our neighborhood. It took a moment to realize that due to a film shoot, the city had turned off all the lights on the main streets. I walked the dog, said "Hi" to neighbors walking down the street, just as normal and safe as a typical night. I snapped some photos. I set the exposure to try and capture the visual quality of the experience (1sec f/3.5 at ISO 800). The lights came back on later in the night and I shot with the scene with the same settings.

This work by Ken Walczak is licensed under
a Creative Commons Attribution 4.0 International License.

This work by Ken Walczak is licensed under
a Creative Commons Attribution 4.0 International License.

Animated version

In an area with significant skyglow, I have often found that you actually have the better vision in unlit areas (e.g. parks, rooftops) than on lit city streets. The reason alleys in big cities are dark is not generally because there isn't enough light for you to see, but because of either glaring lights creating more contrast than your visual system can deal with, or else because you've left a really bright street and your eyes haven't had a chance to adapt.

In case you didn't see it already, check out the other amazing photo of clouds glowing over the Chicago skyline Ken sent me a few months ago.

Wednesday, February 26, 2020

How not to light a staircase

Staircases represent a tripping hazard, and it is therefore not unreasonable to illuminate them under certain circumstances. However, as I have shown in the past, poorly designed illumination is actually much worse than no illumination at all. A (literally) brilliant example of this comes from the "Lustgarten" park in Potsdam:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

These lights combine both the wrong direction (shining horizontally rather than downward) with being extremely bright, which makes them terribly glaring, and makes it harder, rather than easier, to safely ascend the staircase. (Right after I took this photo, I misjudged the position of the first step and stumbled slightly, even though I was trying to shield my eyes from the glare).

What could be done instead? One interesting application I have seen is LEDs installed on the underside of a handrail. Unfortunately, I don't have any photos of a really good execution of this. Here is an example of an attempt that didn't quite work out:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

It's better than the example above, but is still a problem, because it's still too bright near the lamps. What pedestrians need is accent illumination that helps them separate the stairs from the surroundings. When you have most of the scene lit with ~0.1 lux from skyglow and other distant light sources, and you then put 50 lux directly under the handrail, you've now created a 500:1 contrast. Your visual system doesn't deal well with that level of contrast, and it makes it harder to see.

For areas that are not brightly lit, moonlight provides a good benchmark. A typical full moon night is around 0.1-0.2 lux, so if you're illuminating a fairly light concrete, you really shouldn't need any more than that.

Monday, December 2, 2019

Second action of the Nachtlicht-BüHNE outdoor lighting project

Nachtlicht-BüHNE is a co-Designed Citizen Science project related to light at night, funded via the CitizenScience@Helmholtz initiative of the Helmholtz Association in Germany.
Within the project, citizen scientists will be developing two apps. The first, coordinated by the German space agency (DLR), is about improving the system for reporting sightings of fireballs in Germany. The second, coordinated by the German Research Centre for Geosciences (GFZ), is about creating large-scale inventories of all outdoor lighting. This means we are interested not just in street lighting, but also private lights, lighting for advertisement, industrial lighting and so on. For more detailed background, see the previous blog post from September 5th

This work by Markus Schönrock is licensed under
a Creative Commons Attribution 4.0 International License.
To get to the point: there are no exhaustive databases categorizing all outdoor light sources (in contrast to the situation for streetlights, for which there are some public databases). In order to understand the radiance observed by satellites, we therefore need information about what types of light sources are producing the light. We would also like to understand how the types of light source change depending on whether the satellite is viewing a small town, suburban areas, or city centers. This project aims to develop an app to allow citizen scientists to record and count outdoor luminaires, creating one of the first datasets of this kind…you can be part of it!
Before we can develop the app, we need to figure out how to make it work well. We are planning on producing two versions app the app: a Basic version with the minimum requirements, and a Pro version that allows more detailed information to be recorded. We are starting with the Pro version, and this is where we need your help right now:
We have a special form for you to record the data. You should send us your record by January 19th, 2020 to helga.kuechly@gfz-potsdam.de. Also, please feel free to send us your feedback about what worked, what didn’t, and any problems and further ideas you have about our approach.
Here are the detailed instructions:
  • Find a friend
  • Print out our paper form
  • Have a look at the form from start to end, so you that you are familiar with the different categories and attributes of the luminaires. (For example, we also count illuminated windows, which might at first sound crazy, but actually does not take that long and turns out to be really important.)
  • Choose a starting and ending location (typically a single street from one intersection to another).  
  • Get a pencil or pen, and then take the form and meet your friend at the starting location.
  • Write down the time you started.
  • Start walking slowly down the street, recording ALL the light sources you can see. We find it works best for one person to spot the lights, and the other to record which type they are.
  • When you reach your stopping point (eg. the next intersection), write down the time you finished
  • Optional: do another street! (But with a new form, please!)
  • When you get home, type your observations into this Excel form, and save it.
    • Record the coordinates of your segment on the form in decimal degrees (WGS84, for example 52.5163N, 13.3777E). You can find the coordinates using Google maps or Openstreetmap.
  • Send us your data and your thoughts about this paper version to helga.kuechly@gfz-potsdam.de by January 5th 2020.

Finally, some additional hints regarding the lamp categories:
  • Most of the time we count the number of luminaires we see – if a street lamp more luminaires (e.g. a  candle tree with two arms) we count each of them individually (so two)
  • Sometimes counting is not enough in categories where the luminaires vary greatly in size (e.g. illuminated signs outside of shops). In this case, we have three size categories, and you count the times the luminaire fits into them (e.g. a sign roughly as big as two hands counts as two hand-sized signs)
  • Full cutoff luminaires: this is a lighting fixture that projects all of its light in a downward direction – it can sometimes be tricky to tell if a street light is very high up. Here some hints to help you with determining if a light is full cutoff:
    • The light source is fully inside of the fixture, it does not hang below it.
    • The glass below the lamp is entirely flat, not curved
    • The fixture is directed straight downwards (not tilted at an angle) 
    • No light should shine above the height of the lamp (if a nearby house or tree is lit at a level higher than the lamp, it’s not full cutoff) 
  • Normal versus bright: humans cannot reliably estimate small differences in brightness, but we can identify particularly glaring light sources. So we want to record separately light sources that seem particularly bright to you compared to the rest in your street segment (e.g. the lighting at a zebra crossing, an extraordinarily bright shop window or sign etc.) 
Paper form
Excel form
Do not make observations alone! With two people, you will do a better job of keeping track of your surroundings. But it’s also much easier and a lot more fun to do it with a friend or family member! 

This work by Markus Schönrock is licensed under
a Creative Commons Attribution 4.0 International License.

Zweite Aktion des Außenbeleuchtungsprojekts Nachtlicht-BüHNE

[English version here]

Nachtlicht-BüHNE ist ein Co-Design Citizen Science Projekt zum Thema Licht bei Nacht, das über die Initiative CitizenScience@Helmholtz der Helmholtz-Gemeinschaft in Deutschland finanziert wird.
Im Rahmen des Projekts werden Bürgerwissenschaftler*innen zwei Apps entwickeln. Die erste, vom Deutschen Zentrum für Luft- und Raumfahrt (DLR) koordinierte Maßnahme betrifft die Verbesserung des Systems zur Meldung von Feuerkugeln  in Deutschland. Die zweite, koordiniert durch das Deutsche GeoForschungsZentrum (GFZ), befasst sich mit der Erstellung von groß angelegten Katastern der gesamten Außenbeleuchtung. Das bedeutet, dass wir uns nicht nur für Straßenbeleuchtung interessieren, sondern auch für Privatbeleuchtung, Werbebeleuchtung, Industriebeleuchtung etc. Für einen detaillierteren Hintergrund siehe den vorherigen Blogbeitrag vom 5. September (auf Englisch). 

Dieses Werk von Markus Schönrock ist lizenziert unter einer
Creative Commons Namensnennung 4.0 International Lizenz.

Um auf den Punkt zu kommen: Es gibt keine umfangreichen Datenbanken, die alle Außenlichtquellen kategorisieren (im Gegensatz zur Situation bei Straßenleuchten, für die es einige öffentliche Datenbanken gibt). Um die von Satelliten beobachteten Lichtemissionen verstehen zu können, benötigen wir daher Informationen darüber, welche Arten von Leuchten das Licht erzeugen. Wir möchten auch verstehen, wie sich die Arten von Lichtquellen ändern, je nachdem, ob der Satellit eine Kleinstadt, Vorstadtgebiete oder Stadtzentren betrachtet. Ziel dieses Projekts ist die Entwicklung einer App, die es Bürgerwissenschaftler*innen ermöglicht, Außenleuchten aufzunehmen und zu zählen, und damit einen der ersten Datensätze dieser Art zu erstellen......und Du kannst ein Teil davon sein!
Bevor wir die App entwickeln können, müssen wir eine gute Methode entwickeln. Wir planen, die App in zwei Versionen zu produzieren: eine Basis-Version, mit den Mindestanforderungen und eine Pro-Version, die es ermöglicht, detailliertere Informationen zu erfassen. Wir beginnen mit der Pro-Version, und hier brauchen wir jetzt Eure Hilfe:
Wir haben ein spezielles Formular für Dich, um die Daten zu erfassen. Du  solltest uns Deine aufgenommen Daten bis zum 19. Januar 2020 an helga.kuechly@gfz-potsdam.de  schicken. Außerdem kannst du uns gerne Dein Feedback darüber geben, was funktioniert hat, was nicht, und alle Probleme und weitere Ideen, die Du zu unserem Ansatz hast.
Hier kommt die genaue Anleitung:
  • Finde eine*n Freund*in 
  • Druckt unser Papierformular aus
  • Sieh Dir das Formular von Anfang bis Ende an, damit Du mit den verschiedenen Kategorien und Eigenschaften der Leuchten vertraut bist. (Zum Beispiel zählen wir auch beleuchtete Fenster, was sich zunächst verrückt anhören mag, aber eigentlich nicht so lange dauert und sich als sehr wichtig erweist.)
  • Wählt einen Start- und Endpunkt (typischerweise eine einzelne Straße von einer Kreuzung zur anderen). 
  • Hol Dir einen großen Notizblock und einen Stift, und treffe dann Deine*n Freund*in am Startort und schreibe die Zeit auf, die Du begonnen hast.
  • Gehe langsam die Straße hinunter und nehme ALLE Lichtquellen auf, die Du sehen kannst. Es funktioniert am besten wenn eine Person die Lichter aufnimmt, und die andere aufzuzeichnen, welcher Typ sie sind.
  • Wenn Du Deinen Haltepunkt erreichst (z.B. die nächste Kreuzung), notiere Dir die Zeit, in der Du fertig warst.
  • Optional: Mache eine weitere Straße!
  • Erfasse die Koordinaten Deines Segments in Dezimalgraden (WGS84, z.B. 52.5163N, 13.3777E). Du kannst die Koordinaten z.B. über Google Maps oder Openstreetmap finden.
  • Wenn Du nach Hause kommst, gib Deine Beobachtungen in dieses Excel-Formular ein und speichere es.
  • Senden uns Deine Daten und Deine Gedanken zu dieser Papierversion bis zum 5. Januar 2020 an helga.kuechly@gfz-potsdam.de  

Abschließend noch einige zusätzliche Hinweise zu den Lampenkategorien:
  • Meistens zählen wir die Anzahl der Leuchten, die wir sehen - wenn eine Straßenlampe mehrere Leuchten hat (z.B. eine Armleuchte mit zwei Armen), zählen wir jede von ihnen einzeln (also zwei).
  • In Kategorien, in denen die Leuchten sehr unterschiedliche Größen haben (z.B. Lichtwerbung außerhalb von Geschäften), reicht die Zählung manchmal nicht aus. In diesem Fall haben wir drei Größenkategorien, und wir zählen die Anzahl der Kategorie, in denen die Leuchte passt (z.B. ein Leuchtschild, das etwa so groß wie zwei Hände ist, zählt wie zwei handgroße Zeichen).
  • Voll abgeschirmte Leuchten: Dies ist eine Leuchte, die ihr gesamtes Licht nach unten projiziert - es kann manchmal schwierig sein zu erkennen, wenn eine Straßenleuchte sehr hoch steht. Hier einige Hinweise, die helfen, festzustellen, ob eine Leuchte voll abgeschnitten ist:
    • Die Lichtquelle befindet sich vollständig im Inneren der Leuchte, sie hängt nicht darunter.
    • Das Glas unter der Lampe ist völlig flach, nicht gebogen.
    • Die Vorrichtung ist gerade nach unten gerichtet (nicht schräg geneigt).
    • Kein Licht sollte über die Höhe der Lampe hinaus leuchten (wenn ein Haus oder Baum in der Nähe auf einem höheren Niveau als die Lampe beleuchtet wird, ist es keine vollständige Abschaltung).
  • Normal versus hell: Der Mensch kann kleine Helligkeitsunterschiede nicht zuverlässig abschätzen, aber wir können besonders grelle Lichtquellen identifizieren. Deshalb wollen wir separat Lichtquellen aufzeichnen, die im Vergleich zum Rest des Straßenabschnittes besonders hell erscheinen (z.B. die Beleuchtung an einem Zebrastreifen, ein außergewöhnlich helles Schaufenster oder Schild usw.).


Mache keine Beobachtungen allein! Mit zwei Personen könnt ihr besser die Umgebung im Auge zu behalten. Und es ist auch viel einfacher und macht viel mehr Spaß, es mit einem Freund*in oder Familienmitglied zu machen!
Dieses Werk von Markus Schönrock ist lizenziert unter einer
Creative Commons Namensnennung 4.0 International Lizenz.

Monday, November 25, 2019

Skyglow hotspots over Chicago

Ken Walczak took this photo of the glowing sky above Chicago's skyline from the base of the Adler Planetarium:

This work by Ken Walczak is licensed under a
Creative Commons Attribution 4.0 International License.

The bright spots show up where near vertically upward directed light enters a cloud. The lights that cause the bright patches are poorly directed, missing their target, contributing to light pollution, and wasting energy without providing any social benefit. Some countries and cities have enacted lighting ordinances or laws that do not allow this kind of lighting. With clever design, it's possible to light building facades without spilling light directly into the sky, saving energy, reducing light pollution, and reducing impacts on wildlife like migrating birds.

Kornél and Zoltán Kolláth have shown that if you know the distance to the buildings, you can use the positions of these glows to calculate how high the cloud base is. In principle, you could use the same method in reverse to figure out which buildings are responsible! But if you're from Chicago, maybe you already have a guess? Feel free to leave your guesses in the comments.

Wednesday, September 18, 2019

Bad lamp workarounds

Have you ever seen a badly designed or implemented outdoor lamp, and then actually done something about it? I've actually done this twice with floodlamps that were meant to illuminate buildings but were not well aimed. Just a little tilt, and suddenly all the light is on the building and no longer streaming into the sky... 

Here's a great example photographed by Tatjana Scheffler showing how someone decided to deal with a problematic buried spotlight:

This work by Tatjana Scheffler is licensed under a
Creative Commons Attribution 4.0 International License.

The problem was that when you go to to get your bike, the lamp shines up into your eyes and is very disturbing. Whoever found the pylon "solved" the problem for at least a portion of the bike parking area. Of course, this meant that the pillar was no longer floodlit, so this is a more drastic change than what I was talking about above.

Still, if light art is going to be used, it ought to be beautiful. And not just for the cars that are driving past, but for the customers that are shopping in the store employing the light art!

Thursday, September 5, 2019

First action of the "Nachtlicht-BüHNE" lamp project

I'm very excited to announce that the Helmholtz Association has decided to fund a new project related to light at night, called Nachtlicht-BüHNE. It is a co-designed citizen science project, funded under the CitizenScience@Helmholtz funding initiative.

BüHNE stands for "Bürger-Helmholtz-Netzwerk für die Erforschung von nächtlichen Lichtphänomenen". That translates roughly to the "citizen/Helmholtz network for the study of night light phenomena. The German word Bühne means "stage", and citizen scientists will really be at center stage in the project.

Within the project, citizen scientists will be developing two apps (in cooperation and consultation with the project coordinators). The first, coordinated by my colleague Friederike Klan at DLR, is about improving the system for reporting sightings of fireballs in Germany. The second, coordinated by me at GFZ, is about creating several large-scale inventories of ourdoor lighting. That's the part I am writing about in this post.

Our previous research has shown that light emissions are growing at a rate of over 2% per year worldwide, including in wealthy countries like Germany. The problem is, we don't know what types of lamps are responsible for the growth. For that matter, when we look at low-resolution satellite imagery, we don't even know what types of lamps are responsible for the emissions.

Composite image of Berlin from the Suomi NPP Day/Night Band.

Even with higher resolution imagery from space or the air, we still can't tell how much light comes from, for example, street lamps compared to advertising lighting:

Berlin photographed from the International Space Station.

Our goal within the artificial light part of Nachtlicht-BüHNE is to obtain more complete information from the ground that we can use to improve our understanding of the satellite imagery. For example, when the DNB instrument in space says that the radiance is "35 nW/cm2sr", how many light sources on the ground are responsible for it? 100? 1000? And how do the types of light sources change depending on whether you are in a small town, the suburbs, or a city center?

In the Nachtlicht-BüHNE lamp project, large teams of citizen scientists will work together to count all of the lamps that are visible from public spaces over very large areas. By the project end, we expect to have at least 3 regions in which we have counted all of the light sources visible from public spaces covering 2km2. Of course, we hope that the teams of citizen scientists will manage more than 3 regions, and maybe even larger areas, but that's getting ahead of ourselves...

Before we can develop an app, we need to figure out how to make it work well. Our first goal is therefore to start building up categories of what types of lamps are out there. It's easy to think of some obvious frequent types: street lights, illuminated windows, bus shelters, lit advertising, facade lighting. But there's a lot more! Gas station canopies, strings of lanterns, in ground luminaires, porch lighting...

The list goes on and on (and on and on), so in order to make sure we cover everything, and even more importantly, to make sure we organize things logically, we're going to need input from you. For the next 10 days, we're asking people around the world to go out at night and walk short transects with a friend, recording light source types, counting the number of each, and recording how long it takes

Here's what we suggest you do:
  • Find a friend
  • Choose a starting location together (eg. an intersection)
  • Get a large notepad and a pencil or pen, and then go to the starting location
  • Note the time
  • Start walking slowly down the street
  • Have your friend call out the different lamp types he or she sees, while you start recording them on a table
  • When you reach a logical stopping point (eg. the next intersection), write down the time you finished
  • Optional: do another street!
  • When you are finished, go home and report the data to us using this form in English (or this form for German)
  • Let us know your thoughts about the project from within the form, including ideas about how the app might work
    •  Note: DO NOT put your name, email, or any identifying information in the form! We want the data to be completely anonymous at this stage so that we can easily share it with our citizen scientist team without any privacy concerns. But we do welcome your correspondence. You can comment on this blog post, or contact Helga Kuechly at the email address at the bottom of the online form.
    • Do not make observations alone! With two people, you will do a better job of maintaining situational awareness. It will also be a lot more fun with a friend! 
    • If you live in an area with aggressive policing, we recommend you do not take part in this phase. Please wait until we have a printed form or the app which you could show to any police officers who wonder why you are taking notes about a neighborhood at night.

You can categorize the data in any way you want. Should you keep track of the color of the lamps? The height of the poles? How bright they seem? Whether they emit light upwards? It's entirely up to you! Do what you think is logical, needed, and/or easy. Our aim is to develop a system that provides useful data while also being really easy for anyone without background in outdoor lights to take part.

We are accepting data in this test phase until September 15. Our plan is then to meet with our team of citizen scientists developing the app to develop a standardized paper form, and then in late September or early October we'll run another campaign to see how well the standardized form works.

If you can speak German and would like to be part of the team of citizen scientists doing the app development and testing, please contact Helga Kuechly. Please also contact Helga if you would like to arrange an observation campaign in your community (no German required!), or help develop an English version of the app. If you would like to get our project newsletter by email, you can sign up here

Data submission form in English // data submission form in German