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Nighttime light remote sensing means the process of remote sensing satellites recording visible radiance source information from land/water at cloud-free nights. Most of this kind of light information emitted by human activities on the earth, mainly human night lighting, such as city light; At the same time, oil and gas burning light, fishing boat light, marine life light in nature, forest fire and volcanic eruption light is also part of luminous source.
Compared to daytime remote sensing, nighttime light remote sensing provides a unique perspective on human social activities. Information.By mining data on night-time remote sensing images, you can discover the following knowledge:Estimation of socioeconomic parameters (population, GDP, electricity consumption, etc.), urbanization monitoring and evaluation, major event assessment (crisis, natural disasters, war, humanitarian disasters, etc.), eco-environmental assessment and health effects research, including light pollution analysis and its medical and ecological effects analysis and so on.
I. Estimation of socioeconomic parameters
Socioeconomic parameters are of great value to government decision-making and scientific research. While due to the limitations of traditional statistical survey methods, the acquisition of socio-economic parameters often has shortcomings such as large errors and lack of spatial information. There is a high correlation between nighttime light remote sensing images and human activities, and the images have the advantages of time and space continuous, independent and objective. Luminous remote sensing images can further estimate key socio-economic parameters such as GDP(gross national product), population distribution, energy consumption, carbon dioxide emissions, poverty, and freight volume in the observed area, providing an important basis for these parameter estimates.
The spatialization of population data is extremely important for providing key parameters for regional economics, disasters, global changes, etc. Studies have found that population density can be studied using nighttime light images, simultaneously, combined with nighttime light data and auxiliary data, population data spatialization research can be carried out. Brazil, the European Union, China, Italy and other countries have also done a lot of research based on different geographic information and remote sensing data, and confirmed that the spatial distribution map of population produced by nighttime light remote sensing images has a good correlation with the spatial distribution of actual population.
Source：SATELLITE IMAGERY FOR STUDYING DEVELOPMENT?THE ITALIAN CASE STUDY[J]
2. Estimation of gross national product
The density and use of lighting can reflect the prosperity of the region. A large number of statistical studies have shown that the brightness of nighttime lights is highly correlated with GDP(gross national product ) or GRP (gross regional product). This results have been confirmed by different research analysis of the EU, China, and the United States. In the article Using Luminosity Data as a Proxy for Economic Statistics, the researcher used the 1992-2008 luminous remote sensing data to revise global GDP grid products, found that the nighttime light data can play a very significant role in estimating the GDP of countries with missing statistics.
Source: THE VALUE OF LUMINOSITY DATA AS A PROXY FOR ECONOMIC STATISTICS
3. Electricity consumption estimation
Nighttime luminous images can reflect the density and usage amount of lighting facilities, therefore, it can also provide a basis for the spatialization of power consumption. Literature Estimating Energy Consumption from Night-time DMPS/OLS Imagery after Correcting for Saturation Effects proposed to use nighttime light data to measure and calculate power consumption. Researchers have done regression analysis of electricity consumption and total luminous output in dozens of Asian countries such as Japan, China, and India, and have found that the accuracy rate reached 60%, which proved the rationality of estimating the electricity consumption using nighttime light. Literature Detection of Rural Electrification in Africa using Night Lights Imagery, based on multi-source luminous images, studied the relationship between rural electric power penetration and nighttime light in Senegal and Mali through a large number of ground investigations and found that the night light of the electrified village is significantly higher than that of the unelectrified village, which proved that night light images can be used to detect global electric power penetration.
Location of villages in study, Senegal. Surveyed electrified villages in green (n=202). Control group of unelectrified villages in red (n=800). Background image shows 2009 stable lights annual composite from the F16 satellite.
Source:Detection of Rural Electrification in Africa using DMSP-OLS Night Lights Imagery
4. Carbon emission estimation
We all know that carbon emissions are closely related to human economic activities, and economic activity has a strong correlation with night light. Therefore, nighttime light can be used to reflect the spatial distribution of carbon emissions and to spatialize carbon emissions. Literature Creating a Global Grid of Distributed Fossil Fuel CO2 Emissions from Nighttime Satellite Imagery proposes to use nighttime light data to allocate carbon emission data in nighttime lighting areas and using population data to allocate carbon emissions data in non-lighted areas, and generated a global carbon emission grid map with a resolution of 1km × 1km. The results show that the method is more accurate than the carbon emission grid map generated by using the night light data alone.
Estimated CO2 emissions grid in tonnes /km2/year
Source: Creating a Global Grid of Distributed Fossil Fuel CO2 Emissions from Nighttime Satellite Imagery
In view of the high correlation between nighttime light, population and economy at different scales, nighttime light provides a new way for the spatialization of social and economic indicators.
II.Urbanization monitoring and evaluation
The use of luminous remote sensing can intuitively reflect the spatial expansion process of urbanization construction, which helps people to analyze the evolution law of urban agglomeration and urban spatial structure.
1. Urbanization monitoring
Luminous remote sensing images reflecting the characteristics of human activities provide an accurate, direct, economical and time-saving method for urban expansion monitoring. The built-up area is an important parameter of urbanization. Studies have shown that luminous images can effectively extract the scope and changes of built-up areas. Therefore time series nighttime light images can reflect the dynamic information of urbanization. Kazakhstan and China have also conducted relevant research, and the results have proved that time series luminous images can better reflect the dynamic changes of urbanization.
Urban monitoring requires luminous image data with high spatial resolution to support, making the monitoring clearer and more accurate. Also color luminous images will better support analysts to do identification, which will help a lot to the accuracy.
Source: Spatial Pattern Evolution and Optimization of Urban System in the Yangtze River Economic Belt, China, Based on DMSP-OLS Night Light Data
2. Analysis of the evolution of urban agglomerations and urban systems
Luminous images can be used not only to monitor urbanization, but also to explore the temporal and spatial evolution patterns of urban agglomerations. Literature Mapping and Evaluating the Urbanization Process in Northeast China Using DMSP/OLS Nighttime Light Data analyzed the expansion characteristics of the Yangtze River Delta urban agglomeration using nighttime light images from different years. Researchers discovered three urban expansion models in the region and concluded that the imbalance of urban development within the region is gradually decreasing. As a research data supporting analysis of the evolution of urban agglomerations and urban systems, high spatial resolution nighttime light images will make the analysis results more accurate.
Source: Mapping and Evaluating the Urbanization Process in Northeast China Using DMSP/OLS Nighttime Light Data
III. Major Event Evaluation
We found that dramatic reductions or fluctuations of the nighttime light often mean local wars, humanitarian disasters or natural disasters.
1. Monitoring of crisis and natural disasters
Literature Brazil’s 2001 Energy Crisis Monitored from Space used the night light image to study the Brazilian energy crisis in 2001. During this period, Brazil’s electricity consumption has decreased by 20%, and the luminous brightness has also decreased by about 20%, which proved that luminous images can monitor energy crisis. Luminous images can also be used to assess the extent of natural disasters, this was verified in literature Early Damaged Area Estimation System Using DMSP-OLS Night-time Imagery.
Figure 8 Pre-event
Figure 9 Post-event
Source: Early Damaged Area Estimation System Using DMSP-OLS Night-time Imagery
2. Monitoring of war and humanitarian disaster
Luminous images can also detect large-scale humanitarian disasters and war situations. In terms of war, by comparing the 2011 nighttime light remote sensing image of Syrian with that of the post-war Syrian, we can see that the night light is reduced by 80%. The study concluded that there is a high correlation between the reduction in luminous and the number of refugees. Where the amount of night light reduction is large, the number of refugees has risen sharply, from which the severity of the Syrian war can be estimated.
For war and disaster monitoring, luminous remote sensing satellite with a short revisit cycle will help you analyze the situation immediately.
Luminous remote sensing images before and after the Syrian war in 2011 and 2015
Using luminous remote sensing images as the main data source, it can also quickly estimate the ecological environment, accurately assess light pollution, efficiently capture marine fishery activities, and quantitatively assess the impact of human activities on coral reef ecologically fragile areas.
IV. Ecological Environment Assessment and Health Effects Research
Luminous remote sensing images can be used to study ecological environment and health issues. On the one hand, urban expansion is accompanied by a series of ecological and environmental problems, then luminous images can be used as one of the data sources for evaluating these problems. On the other hand, urban nighttime light not only symbolizes economic prosperity, but also causes light pollution, so nighttime light images can also be used to monitor light pollution and its health effects.
1. Analysis of the environmental effects of urban expansion
Night lights not only directly reflect the urbanization process, but also can assess the ecological and environmental issues caused by urbanization. A large number of literature studies have shown that luminous images combined with ecological data can be used to analyze the ecological effects of urbanization, to assess the fire risk of urban expansion, and the loss of animal habitat due to urban expansion.
Source: Exurban Change Detection in Fire-Prone Areas with Nighttime Satellite Imagery
2. Light pollution and effect analysis
Investigate the distribution of light pollution with through remote sensing technology is a fundamental task. The nighttime light has brought convenience to humans, but also brought a negative impact on various organisms that have adapted to nature. For example, light pollution is caused by excessive use of nighttime lights. American studies have found that light pollution is positively correlated with the incidence of breast cancer and prostate cancer, and the proportion of adolescent night personality. Also studies have shown that light pollution also changes the nesting habits of sea turtles and the living habits of some birds. The development of luminous remote sensing technology enables light pollution research to be carried out in a large space.
Source: Urban expansion dynamics and natural habitat loss in China: a multi-scale landscape perspective
Using luminous images for eco-environmental assessment and health effects studies, the higher the spatial resolution, the more accurate the analysis results.
Town lights are the main source of nighttime lights on land, while fishing boats are the main source of oceanic nightlights. In many countries, the fishermen load huge-powered lighting bulbs on fishing boats taking advantage of the nighttime phototaxis of some marine life. Therefore, fishery activities can be carried out efficiently, which provides the possibility of obtaining fishery information using nighttime light remote sensing images. For example, the time and space distribution information of the team can be obtained, and the fishery law is found that the fishing range and the catch are positively correlated. From this, we can speculate on the migration range of the fish population, etc. (See details in literature Technical Note and Cover Fishing Fleet Lights and Sea Surface Temperature Distribution Observed by DMSP/OLS Sensor)
Source: Illuminating the Capabilities of the Suomi National Polar-Orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band
VI. Other research
In addition to the above studies, luminous remote sensing has played a role in research fields such as epidemiological research, oil and gas field monitoring, and forest fire monitoring. A research paper entitled “Explaining Seasonal Fluctuations of Measles in Niger Using Nighttime Lights Imagery” was published in the journal Science in 2011. The author has used seasonal changes in urban nightlights to characterize the dynamics of urban populations and found that the measles infection in Niger, Africa can be explained by the change of luminous light. It is revealed for the first time that the outbreak of the disease comes from the population aggregation effect, which proves that nighttime light remote sensing can be used in public health research. It revealed for the first time that the outbreak of the disease comes from the population aggregation effect, which proves that nighttime light remote sensing can be used in public health research.
VII. How to get a night light image that meets the above purposes?
The above-mentioned various fields require different parameters of the nighttime light image, including: color luminous image, high spatial resolution, short revisit period and high performance cost ratio and other advantages.
The “Jilin No.1” constellation Changguang Satellite developed and operated has 10 in-orbit commercial high resolution satellites, which can revisit the same spot twice per day. Its color luminous images have a spatial resolution of up to 0.9m, which is not available from other companies. Also it supports 120-second 4K HD gaze color videos of resolution less than 1m. 11km × 4.6km swath width makes shooting at the observation site more efficient, and also delivery time shorter. The imaging side swing angle can be customized according to user requirements, and the product grades provided are L1A, L2. The exclusive supplied luminous images is a boon for business consulting companies, satellite image processing processors and researchers.
The following are the nighttime light images of different cities taken by the Changguang Satellite “Jilin No. 1” constellation for your reference.
Hong Kong, China
Huairou, Beijing, China
Nanchang City, China
For more information, please refer to web：www.cgsatellite.com