Help using lightpollutionmap.info

Table of contents

About

Navigation

Changing map content

Toolbar

Extended toolbar

Other functionalities

FAQ

Support

Privacy policy

About

www.lightpollutionmap.info is a mapping application that displays VIIRS/DMSP/World Atlas overlays/IAU observatories and the user measurements overlay over Microsoft Bing base layers (road and hybrid Bing maps).

The primary use is to show VIIRS/DMSP data in a friendly manner, but over time it also included some other interesting overlays that concern light pollution like SQM/SQC, World Atlas 2015 zenith brigtness, clouds and IAU observatories. If you have a permanent SQM reader installed you can add it to the map by contacting me.

Annual VIIRS comparisons are to be avoided as there are too many factors involved by just doing a direct comparison. If you want an analysis of radiance (VIIRS/DMSP) changes over a period of time, then please use the Lighttrends application.

Data for observatories sourced from Wikipedia. If you want to contribute to the list, you can do so by editing this document

VIIRS/DMSP data credits: Earth Observation Group, NOAA National Geophysical Data Center.

World Atlas 2015 data credits: Falchi, Fabio; Cinzano, Pierantonio; Duriscoe, Dan; Kyba, Christopher C. M.; Elvidge, Christopher D.; Baugh, Kimberly; Portnov, Boris; Rybnikova, Nataliya A.; Furgoni, Riccardo (2016): Supplement to: The New World Atlas of Artificial Night Sky Brightness. GFZ Data Services. http://doi.org/10.5880/GFZ.1.4.2016.001
Falchi F, Cinzano P, Duriscoe D, Kyba CC, Elvidge CD, Baugh K, Portnov BA, Rybnikova NA, Furgoni R. The new world atlas of artificial night sky brightness. Science Advances. 2016 Jun 1;2(6):e1600377.

You can support the authors of World Atlas 2015 by visiting: The New World Atlas of Light Pollution - Paperback and buying it on Amazon

Send comments about the map and suggest new features to Jurij Stare

Navigation

Panning

Left click and drag the map in desired direction or slide your finger if you are using a touchscreen capable device.

Change zoom

Use mouse scroll wheel to change zoom or press +/- buttons on the toolbar. You can also zoom to a desired rectangle by drawing it using shift-left mouse drag. Another way to zoom in is to just double-click the map and it will zoom-in.

Changing map content

The right menu contains controls which you can use to change map contents and view the legend. The menu can be hidden or displayed by clicking on menu button in the top right corner. You can click on the “i“ icon to get additional information about data displayed,

Overlays, features and base map

The “Map layers” section of the right menu contains controls which enable you to select a desired overlay, features and base map. Overlay and features have a slider below the selection which you can use to change its opacity. The default opacity is set at 60%. Base

There are two base layers available, Bing Road and Hybrid which is a mix between Satellite and Road type map. These two base maps are provided by Microsoft REST service.

Clouds options

When you have clouds overlay selected, there are two additional controls next to the dropdown menu.
The play icon creates a cloud animation of the last 12h.
Clicking the hour label changes the animation loop speed (it iterates over 4 different speeds, max speed by default).

SQM/SQC/Observatories options

click on the “cog wheel” to display additional options for the selected feature. You can ie. filter SQM points by the name or date. Observatories option contains additional fields used for finding them and assessing their light pollution levels

Map legend

Shows the legend of the currently visible overlay and feature.

My locations

You can create a list of locations to quickly access them later. To start making an entry click on "Edit". When you click on the "New" button, a new entry will be created (it creates a snapshot of your current map position). You can name it, reposition it (click & drag far left button up/down) or delete it (far right button). Optionally you can add a pushpin to desired coordinates by clicking the pushpin icon (located between name and delete button), then click on the map. Click "Edit" again to exit the edit mode. The list is saved in a cookie on the device where it was created.

Toolbar

The toolbar contains basic tools listed below.

Zoom-in

Zooms in the map.

Zoom-out

Zooms out the map.

Geolocation

Positions the screen where the user is located. The location is provided by a HTML5 Gelocation API using GPS, GeoIP, Cell network or other means.

Ruler

Measure the distance and azimuth. Left click to start the measurement, double click to end.  Azimuth is available if the line is not segmented and it represents the angle from start of the line to the end. Multiple measurements are supported. To clear all measurements, click again on the ruler icon to deactivate it.

Radiance statistics per country

Displays the statistics of VIIRS data per country land and territorial waters for each year.

Print

Prints the map to a PNG image.

Extended toolbar

Shows or hides the extended toolbar. The extended toolbar can be repositioned by grabbing it by its right side frame.

Help

Shows this document.

Extended toolbar

The extended toolbar contains various measurement tools and tools for adding your own measurements. You can reposition the toolbar by grabbing it by its right edge and move it.

Point information

Left clicking on the map shows a popup displaying clicked coordinates (WGS84 coordinate system in degrees, minutes, seconds format), value of the visible VIIRS/DMSP overlay and elevation (250m SRTM 4 http://srtm.csi.cgiar.org) in meters at clicked location. For World Atlas there is a bit more information available. If no other control is active, this is the default control when left clicking the map unless SQM/SQC layer is visible. In such case SQM/SQC info is shown first if cliking on a SQM/SQC point.

Area information using a polygon

Displays statistics of visible VIIRS/DMSP/WA layer that intersects the drawn polygon. To draw the polygon use left clicks and double left click to finish. The resulting popup can be moved by grabbing its’ frame and repositioning it. The Raw GeoTIFF button will export the original raw data clipped by the polygon. The RGB GeoTIFF button will export the RGB data clipped by the polygon. Export is not only available for World Atlas overlay.

Area information using a circle

Displays statistics of visible VIIRS/DMSP/WA layer that intersects the drawn circle. To draw the circle left click, then move mouse and then left click to finish at desired radius. The resulting popup can be moved by grabbing its’ frame and repositioning it. The Raw GeoTIFF button will export the original raw data clipped by the polygon. The RGB GeoTIFF button will export the RGB data clipped by the polygon. Export is not only available for World Atlas overlay.

Add a marker

By left clicking the map it adds a pushpin marker on the map. To remove markers, left click on them.

Add a SQM measurement

Activating this option enables you to add your own SQM (what's an SQM?) measurement to the map.

"Name or location" should contain your name or place name (non-obligatory field).
Local Date/Time field should contain local time (very important!) the measurement was taken. You can either select the date from calendar applet or enter it manually. Must be in YYYY-MM-DD HH:mm format.
SQM value contains the value.
Make sure you check either SQM or SMQ-L device used.
Comment should contain your comments about the measurement or additional information about the place or weather conditions (non-obligatory field).
Press submit to submit the form.

If successful, the form will close and show you your added measurement. Make make sure a filter in SQM options is not active and possibly hiding the added point. Added points cannot be edited or deleted by you, so double check data you enter.

Other functionalities

Search places

Located on the upper left corner of the map. Enter a place and by selecting it from a dropdown menu it will reposition the map to it. It is also possible to enter coordinates manually in a “latitude, longitude” format and selecting it from a dropdown menu which will zoom to those coordinates.

Scale bar

Located on the bottom left corner of the map. Shows the current map scale

Coordinate display

Located on the bottom right corner of the map. Shows the current coordinates of the mouse cursor or last touch if you are using a touchscreen device. Left click on the coordinate display toggles between decimal and degrees/minutes/seconds display modes.

Toggle right menu

Located on the upper right corner of the right menu. Shows or hides the right menu.

Share map view on social media

Located under the right menu. A quick way to share the current view of the map on certain social media web sites.

Attributions

Located on the bottom left corner of the map. Shows attributions associated with visible overlays and base layers.

FAQ (frequently asked questions)

1.  Why is Canada lit up like a christmas tree?

Two words. Aurora borealis

2.  Why is on ie. VIIRS 2014 overlay less light pollution than on 2013? Isn't it supposed to get worse each year? Then again 2016 compared to 2017, the 2017 is a lot worse!

There are numerous reasons for this. One could be lack of good data. For example some areas have always some clouds and as VIIRS overlay is composited monthly, it is impossible to get good quality data coverage for that month. It is also possible that the proccess used to make the global image is not perfect. It could simply be that the radiance actually decreased or that HPS lamps have been replaced by high color temperature LEDs to which VIIRS sensor isn't too sensitive.

3.  Why are swath trails visible on some VIIRS maps?

Maybe because of not perfect onboard calibration? Best to direct the question to NOAA.

4.  What's an SQM?

SQM stands for Sky Quality Meter. It's a small device that can measure sky quality ie. darkness. It's widely used by amateur astronomers because it's fairly cheap and gives you fast results which can be easily compared to other SQM users. Be aware that two versions exist (SQM and SQM-L) and their readings are not comparable. More about the SQM product visit the manufacturer website.

5.  How can I add my own SQM data?

To add your SQM measurements click on the +SQM icon in the extended toolbar. Please note that the time entered should be your local time the measurement was taken. The only mandatory fields are time and the SQM measurement

6.  What's an SQC?

SQC stands for Sky Quality Camera. It's a calibrated Canon dSLR with a fisheye lens bundled together with a software suite. It produces a 360 degree all-sky image with MPSAS (magnitudes per square arc second) or CCT (color temperature of a black-body radiator) measurements. The result adds another dimension to a standard SQM measurement. More about the SQC product contact Andrej Mohar.

7.  How can I add my own SQC data?

Adding SQC measurements is done through SQC software.

8.  I have hundreds of measurements. How can I submit them all easily?

If they have at least coordinates, date/time, then contact me.

9.  What is the map projection?

The original VIIRS/WA data is in a WGS84 geographic coordinate system. To have it display as overlays on top of Bing maps the data needs to be projected to a Spherical Mercator projection. When you export VIIRS to raw GeoTIFF the data is in the original WGS84 coordinate system.

10.  What is the resolution of the overlays?

The original VIIRS data has a resolution of 15 arc seconds, while World Atlas has 30 arc seconds for each pixel. When projected the resolution is around 500m for each pixel for VIIRS and 1000m for World Atlas. When you use measurement tools in the extended toolbar and zoom in close enough, you will see a faint red grid which represents individual data pixels.

11. How do you convert VIIRS data to MPSAS (magnitudes per square arc second) or Bortle scale? What does W/cm2 * sr mean anyway?

W/cm2 * sr is a SI radiometry unit for radiance. Radiance is radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. It sounds complicated right? Well that's because it is. Things get a bit more (actually a lot more) complicated if you want to do a simple conversion to MPSAS. I'm not even going to touch the Bortle scale issue because it is highly subjective scale. Anyway if you are still interested in a "conversion" I can try to explain the problem. Imagine you have a small light source aimed at the sky and this light source gets picked up by the VIIRS detector detector. The VIIRS detector is monochromatic and has its own spectral response curve. It has no idea of the spectral curve of the light source. MPSAS or more specific magnitude is a measure that is measured in a “specific wavelength or passband”. See the problem? That's one major issue. The other major issue is that light from the light source passes through the atmosphere and while doing this it scatters due to air molecules and aerosols. So you need to create a model of light propagation for the entire Earth taking into the account local air conditions, earth curvature, light absorption, Earth terrain and what not. You can read more about it here. If you got skills to do this and willing share the result I'll be glad to include it! If not be sure to check the World Atlas (WA 2015) overlay.

12. Where was the data sourced?

VIIRS overlays are made from avaraging monthly VIIRS DNB Cloud Free Composites (vmccfg conf) and applying zero point calibration (paper). If you want to view or inspect monthly VIIRS composites then use the Lighttrends application.

World Atlas 2015 overlay data is sourced from http://doi.org/10.5880/GFZ.1.4.2016.001

SQM and SQM-L layers are partially sourced from Unihedron database, the rest from lightpollutionmap.info users.

SQM-LE layer contains permanent SQM-LE installations submited by users. How to submit yours see FAQ #24.

SQC layer contains measurements submited by users of SQC (sky quality camera).

Observatory data is sourced from Wikipedia. Be advised that coordinates may be a bit off (see FAQ #25).

Cloud layer is made from data found on the public websites of the following organisations: EUMETSAT, NOAA, MOSDAC/SAC/ISRO and CIRA.

13. How can I view the raw VIIRS data from NOAA/EOG website? The files are too big to be opened by Photoshop or similar software!

To work with this kind of data you need to have GIS software installed (QGIS, uDig, ArcGIS, etc...)

14. How should I credit the use of www.lightpollutionmap.info data or images (screenshots)?

On the map there is an "i" button on the far bottom left. Clicking it will show you how to credit the current map view.

The use of data from www.lightpollutionmap.info should be credited to "Jurij Stare, www.lightpollutionmap.info".
If VIIRS data is used or displayed it should also include "Earth Observation Group, NOAA National Geophysical Data Center".
If World Atlas data is displayed it should also include "Falchi, Fabio; Cinzano, Pierantonio; Duriscoe, Dan; Kyba, Christopher C. M.; Elvidge, Christopher D.; Baugh, Kimberly; Portnov, Boris; Rybnikova, Nataliya A.; Furgoni, Riccardo (2016): Supplement to: The New World Atlas of Artificial Night Sky Brightness. GFZ Data Services. http://doi.org/10.5880/GFZ.1.4.2016.001
Falchi F, Cinzano P, Duriscoe D, Kyba CC, Elvidge CD, Baugh K, Portnov BA, Rybnikova NA, Furgoni R. The new world atlas of artificial night sky brightness. Science Advances. 2016 Jun 1;2(6):e1600377."

15. I see the coordinate display is in a decimal format, but can you display them as degrees/minutes/seconds?

Click on the coordinates and it should toggle between those two display modes.

16. What is the precise date when VIIRS satellite data was collected?

"layer VIIRS 2019" data was taken between dates 20190101-20191231
"layer VIIRS 2018" data was taken between dates 20180101-20181231
"layer VIIRS 2017" data was taken between dates 20170101-20171231
"layer VIIRS 2016" data was taken between dates 20160101-20161231
"layer VIIRS 2015" data was taken between dates 20150101-20151231
"layer VIIRS 2014" data was taken between dates 20140301-20141231
"layer VIIRS 2013" data was taken between dates 20130101-20131231
"layer VIIRS 2012" data was taken between dates 20120401-20121231

17. VIIRS version 1 series is run globally using two different configurations. Which one are you using?

I'm using vcmcfg which excludes areas impacted by stray light.

18. Exported GeoTIFF is all black!

Exported GeoTIFF is the raw VIIRS data. VIIRS is in a 32bit floating point pixel type GeoTIFF. Use GIS software (QGIS, uDig, ArcGIS, etc...) to stretch the histogram, reclassify etc...

19. How are the country statistics made?

The calculation is done by using boundaries from GADM database and VIIRS radiance data. Radiance data is derived from averaging monthly VIIRS vcmcfg to get an annual VIIRS composite. From this composite a zero point layer (described in this paper) is substracted to reduce the variability of natural light. Radiance sum is area weighted, so comparison between countries on different latitudes is possible.

Countries with asterisk (*) after their name have a large parts above 55 degrees of latitude where high aurora activity is present which can have a strong influence on radiance values. Some countries like Iceland may be missing because of their high latitude where aurora totally covers them.

20. We want to use your WMS/WMTS service

Contact me and we'll work something out.

21. How do I search by coordintes?

Just enter coordinates into the "Search" field located top left in a "latitude, longitude" format.

22. How was the World Atlas 2015 made?

You can read it in the original article here.

23. What is the difference between VIIRS and World Atlas overlays? They look so different.

VIIRS is radiance map while World Atlas ia a sky brightness map. VIIRS shows you light sources, while World Atlas tells you how dark is the zenith based on a model calculated from VIIRS data.

24. How can add my SQM-LE installation to the map?

First create a regular SQM reading point and then contact me to get a unique key (with instructions) that you use to send readings to the server.

25. Some observatories have their positions way off!

This is intentional. In order to protect the privacy of smaller observatories (under 1m aperture) in remote areas, the locations of those observatories have been "anonymised". If you want the original list, you can access it here.

26. My locations data does not sync between devices!

The website does not store ANY personal information (apart from users willingly posting SQM measurements) and as such "My locations" cannot be shared between devices. You will have to enter them again.

27. How often is the cloud layer updated?

The cloud layer is created every hour at about 15 min past full hour. It takes almost half an hour to collect all the data from 5 different geostationary satellites and process it to make a global image which can then be used on a map.
GOES satellite data (NASA/NOAA) is typically refreshed every 10min (near real time data is freely accessible), but other providers such as EUMETSAT refresh it every hour with up to 2h latency (near real time data is not freely accessible). It's not unusual for EUMETSAT (Europe) or MOSDAC (India) to have old data (more then an hour or two old) on their server at the time I fetch it, but GOES (Americas) and CIRA (east Asia) are updated frequently.

Support

In the last couple of years I have had numerous contributions which helped me with keeeping the site working and developing new functionalities.
Below is a list of people who made a substantional contribution:

H. Bardenhagen
R. Wilson
First Light Optics Ltd
K. Pendoley
A. Dainty
K. Maruf
T. Wellington
C. Voirol
relay2me, LLC
M. Lockett
J. Wischmann
D. Stavrogiannopoulos
A. Dremali
A. Petrie
A. Tsiotos
J. Opie
S. Wallner
L. Tibbals
R. Krcmar

On 24th of July 2019 I have switched funding of the website from donations to advertisements.
This was done because donations in the 2019 didn't even cover the server rent costs.
This action also means the end of acepting donations,
unless you are one of those 14% (average here) of people who use an Adblocker,
but wish to donate, then you can use this Paypal form:

Paypal
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You can also donate via Litecoin if you fancy cryptocurrencies:

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Privacy policy

Privacy policy ie. what data is collected and what is done with it can be read here


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