Nighttime lights: The not-so-dark side of the Earth
The night may be dark and full of terrors for the fans of Game of Thrones, but the good folks at NASA have shown us that our planet is never really that dark. The Earth looks absolutely spectacular when wrapped in ‘night lights’ from human colonies, wildfires, oil wells, auroras, et al. Not to forget the reflection of the stars and the moon off the oceans, ice sheets and clouds… Oh-so-stunning!
NASA has been analyzing these twinkling and flickering lights since 2011 when it launched the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite. The space agency released the first global mosaic of night lights in 2012. The second comprehensive global dataset from 2016 came out last month, and we told you all about it here.
Looking at these images, Esri cartographer John Nelson thought it would be really cool to compare the nighttime lights in the two mosaics and see how the Earth and its people have transformed during this period. So, to draw out patterns of expansion and contraction of illumination, Nelson decided to map the changes in ArcGIS Pro.
Using a simple pixel-difference math bot, the mapping nerd isolated the places where lights have come on (shown in blue) and where they have gone off (displayed in pink) in the past few years. (You can read all about the step-by-step process he followed here.) The places that haven’t changed, like metropolitan city centers, or forests and deserts, remain transparent to show the satellite imagery background.
The resulting glow map reveals quite a few striking changes – some easily explainable, some not. For example, vast expanses of new nighttime light have emerged in India over the last five years, especially at the base of the Himalayas and the southern parts of the country. These can easily be attributed to India’s electrification program for its 600,000 villages.
Some stretches in the UAE and parts of Oman also stand out for shining brightly where the night used to be dark just a few years ago. Nelson believes this light is from the new highway etched out in the desert.
However, not all changes are a testimony of hope and development. The island of Puerto Rico has dimmed significantly, as has Venezuela. Looking at the map, the struggling economies of these nations come conspicuously to mind.
There’s an overall reduction in night lighting in Western Europe also, which is hard to explain. It simply might be due to a disparity in the time when imagery was captured, like a weekday versus a weekend, or winter versus summer. To really connect these changes with specific events or activities, one would actually need to get down to the pixel level and take parameters like the viewing angle into account.
Even then, some changes are so evident, it’s difficult to ignore the most obvious explanation. As Nelson tells in this story map, “Perhaps the most stark example of extinguished nighttime lighting is apparent in war-torn Syria, where nearly all the night lights of population centers and the transportation systems that connect them have been wiped dark. Neighboring Iraq shows similar signs of conflict in the northwest, coupled with massive new illumination throughout the rest of the country.”
What are your observations? Tell us in the comments below!
List of Top 10 Sources of Free Remote Sensing Data
The requirement for high quality remote sensing data is skyrocketing with the surge in the application of remote sensing techniques and with the ‘n’ number of researches carried out each day. Every remote sensing analysis revolves around the term DATA with specified resolution, location, sensor and above all it should be FREE OF COST. Here I have listed some of the top players providing Remote sensing data free of cost.
The USGS Global Visualization Viewer (GloVis) is one of the quick and easy online search and order tool for selected satellite and aerial data, especially for beginners. The instruction for downloading data can be found here.
The products available for download are: Digital Orthophoto Quadrangle (DOQs), EO-1 ALI (Earth Observing-1 Advanced Land Imaging), EO-1 Hyperion (Earth Observing-1 Hyperion), Global Land Survey (GLS), Landsat 4-5 TM (L4-5 TM C1 Level-1), Landsat 7 ETM+ (L7 ETM+ C1 Level-1), Landsat 8 OLI/TIRS (L8 OLI/TIRS C1 Level-1), Sentinel-2, ISRO ResourceSAT 1 and 2 – AWIFS Sensor, ISRO ResourceSAT 1 and 2 – LISS-3 Sensor, GeoEye’s OrbView-3 (OrbView-3).
2. NASA Earth Observation (NEO)
NASA Earth Observation has more than 50 datasets on atmosphere, land, Ocean, energy, environment and much more on a daily, weekly and monthly frequency. The datasets are available in the form of JPEG, PNG, Google Earth and GeoTIFF.
3. USGS Earth Explorer
USGS Earth Explorer will stay the best portal for fetching Remote sensing data for a variety of reasons. Specially, a wide array of satellite and aerial images, a wide range of search criteria and the sequential arrangements of satellite imagery make the Earth Explorer a pro in terms of downloading imageries. USGS grants you full access to NASA’s Land Data Products and Services such as Hyperion’ s hyperspectral data, disperse Radar data and MODIS & AVHRR land surface reflectance.
4. ESA’s Sentinel data
The Copernicus Open Access Hub (previously known as Sentinels Scientific Data Hub) provides complete, free and open access to Sentinel-1, Sentinel-2 and Sentinel-3 user products, starting from the In-Orbit Commissioning Review (IOCR). The ESA’s sentinel data is chasing the USGS Earth Explorer with more bands and crisper resolution.
5. NASA Earth Data
With the retirement of the Reverb data search and discovery system on 1 January 2018, Earthdata Search will be the primary means for searching and discovering NASA Earth observing data. The result will be faster data searches and more relevant search results for EOSDIS data users. Earthdata Search uses Client’s natural language processing-enabled search tool to quickly narrow down to relevant collections as shown in the tutorial.
Similar to NASA Reverb, Earth Data communicates with a plethora of satellites such as NASA DC, GPS satellites, SMAP, JASON, METEOSAT, ALOS, TRMM, Aura, Aqua and much more.
6. NOAA Class
NOAA (National Oceanic and Atmospheric Administration) Class has a distinct online data library system, a pool of free top quality and valuable geographic data sets which set them apart. The Comprehensive Large Array- data Stewardship System (CLASS) is really in a class of its own with abundance of data accumulated from other rich and viable sources such as the US Department of Defense (DoD) Polar-orbiting Operational Environmental Satellite (POES) , Environmental Satellite (GOES) , NOAA’s Geostationary, Operational), and other derived data. However when compared to USGS, NOAA Class is still amateurish.
7. NOAA Digital Coast
If Coastal data is your only requirement, there is no better portal to reach than NOAA’s Digital Coast. Simply define your choice of interest and select from the range of free satellite imagery dataset such as infrared, radar and true colour composite to download. Apart from the coastal data you shall as well get imagery, land cover, elevation, socio-economic and benthic data.
8. IPPMUS Terra
IPUMS Terra integrates population census data from around the world with global environmental data, allowing users to obtain customized datasets that incorporate data from multiple sources in a single coherent structure. The country specific data can be obtained from Terraclip featuring MODIS data.
The Land, Atmosphere Near real-time Capability for EOS (LANCE) supports application users interested in monitoring a wide variety of natural and man-made phenomena. Near Real-Time (NRT) data and imagery from the AIRS, AMSR2, MISR, MLS, MODIS, OMI and VIIRS instruments are available much quicker than routine processing allows. Most data products are available within 3 hours from satellite observation. NRT imagery are generally available 3-5 hours after observation.
10. VITO Vision
The VITO Vision provides coarse vegetation data from PROBA-V, SPOT-Vegetation and METOP. These coarse resolution satellites carves out vegetation patterns of the Earth’s surface. The easy-to-use interface and delivers free low resolution satellite data. This type of data is a good for large-scale applications that doesn’t need the finer details.
Every portal makes registration mandatory to download data. So register and download remote sensing data free of cost 🙂