Night-time satellite images of the Korean peninsula – showing North Korea as a black hole surrounded by the gleaming lights of economic powerhouses like China, Japan and South Korea – have become a click-winning favorite among online media outlets.
Most recently, footage captured from the International Space Station made headlines worldwide with a raw display of disparities between North Korea and its more well-off neighbors.
But while the contrasts apparent in such footage is visually stunning, it is not very informative, according to researchers. “We don’t need satellites to tell us (that) South Korea is more economically developed than North Korea,” said Travis Pope at UC San Diego, adding that “simply comparing North Korea to its neighbors can be either misleading or lead one to make nothing but obvious comments”.
“We don’t need satellites to tell us (that) South Korea is more economically developed than North Korea,”
But if applied correctly, analyses of night-time satellite imagery – so-called ‘luminosity studies’ – can fill an important knowledge-gap about a country on which information is notoriously scarce, as is illustrated by the works of a handful of researchers around the globe.
For countries on which socio-economic statistics are scarce – like North Korea – researchers are in want of indicators that can substitute, or at least add to, traditional data. “Luminosity might serve as a useful proxy for output because it is ‘objectively’ measured, is highly correlated with output, and is universally available for the world except for the high latitudes,” according to a paper written by Yale researchers Xi Chen and William Nordhaus from 2010.
Due to noise in the light signals, light density data as a proxy for Gross Domestic Product (GDP) has limited value for countries with functioning national statistical bureaus. But, according to the paper, for regions with poor data, “luminosity shows considerable promise”.
Recently, researchers have attempted to apply this to the case of North Korea. Travis Pope, along with UCSD professor Stephan Haggard, has been looking into what luminosity data from night-time satellite imagery actually says about the state of affairs in North Korea, as can be viewed in recent posts at the ‘North Korea: Witness to Transformation’ blog.
The data – images from the National Geophysical Data Center’s (NGDC) Earth Observation Group, collected between 1992 and 2012 – are composite images, one for each year, pieced together by a range of momentary shots, allowing the observations to avoid random changes, and to pick up smaller sources of luminosity.
But there are caveats when it comes to using the data. According to Pope, among the biggest of them – a phenomenon called ‘blooming’ – happens when light emanating from one grid cell in the dataset ‘blooms’ into neighbouring cells, causing them to appear lit even when there are no light sources within them. This makes assessments about locations along national borders particularly difficult, Pope said.
There’s also the issue of inter-calibration between the various compund images. Since the sensors picking up the data have not been adjusted to the same measurement standards, it becomes difficult to compare changes in absolute luminosity over time. What is possible, however, is to measure the relative share of total luminosity held by each geographic region, and look at how those ratios develop over time.
Using this method, Haggard and Pope have made approximate inferences with regards to regional developments, comparisons between cities, and urban-rural development gaps, finding increases in economic activity in and around Pyongyang, as well as in areas close to the Chinese border in recent years.
Be sure to read: North Korea by night: the technical side
ADAPTING TO SANCTIONS
In another satellite imagery-based study, Yong Suk Lee, an assistant professor at Williams College in Massachusets, uses time-series of night-time luminosity data to gauge North Korean authorities’ responses to international sanctions.
While Lee said the classic night-time Korean peninsula snapshot has indeed become “a cliché”, he agreed that if such data is put in a proper context, it can contribute nicely to the body of knowledge available about North Korea.
By cross-referencing the data with a sanctions index built around international responses to North Korean provocations, Lee found that additional sanctions appear to increase the gap between urban and rural regions, as measured in luminosity.
“The underlying idea is that the dictatorship will try to shield from the impact of sanctions by diverting resources to the valuable urban sector,” Lee said, noting that the impact seems to be strongest for Pyongyang.
“The underlying idea is that the dictatorship will try to shield from the impact of sanctions by diverting resources to the valuable urban sector,”
More concretely, the study found that the urban-rural luminosity gap increased by an average of 0,74 percent with each new sanction levied – the equivalent of an urban-rural GDP difference of 0,15 percent. In rural areas, this translates into a decrease in luminosity by 0,45 percent, or a 0,09 percent GDP decrease; for urban areas – a luminosity increase of 0,29 percent and a GDP increase of 0,06 percent.
Lee also said that luminosity appears to increase at sites along the border with China when sanctions increase. “This seems consistent with the observations that during hardships, trade with China along the border increases,” he said.
UNSEEN BY NIGHT
The contrast between North Korea and its geographical surroundings has made the image of the Korean peninsula by night a popular one. But while North Korea certainly has low luminosity yields, it is also situated directly next to some of the world’s most thriving economic powerhouses – other countries with comparable rates of GDP per capita and similar population densities are usually located in very different geographical contexts.
“If one were to take North Korea and put it in part of Sub-Saharan Africa, I suspect North Korea would be pretty much indistinguishable to other countries,” Lee said.
But what sets North Korea apart from many other countries is the particular structure of the economy, with substantial activity being channeled through the military – a fact that may make single night-time snapshots like the one frequently featured by media particularly useless.
“If one were to take North Korea and put it in part of Sub-Saharan Africa, I suspect North Korea would be pretty much indistinguishable to other countries,”
“It is hard to think of any country that has diverted more resources to institutions whose specific aim is to avoid satellite detection, namely the military”, said Pope, noting how this makes large portions of the country’s economy unobservable to satellite imagery.
North Korea has also dedicated substantial resources to developing military facilities right next to the South Korean border, an area Pope said is “essentially impossible to analyze” because of the ‘blooming’ issue from South Korean military lights on the Demilitarized Zone.
Another major part of the North Korean economy which isn’t easily captured by night-time imagery is the agricultural sector. Time-series of luminosity data show that Northeast Asia has seen a continuously unfolding explosion of light in past decades – with the exception of North Korea. But, according to a study conducted by two geographers at Lund university in Sweden, that shouldn’t necessarily be seen as evidence of slow economic growth.
By combining night-time satellite imagery with day-time land cover images, the researchers were able to identify pockets of agricultural development, and also further corroborate the widely otherwise documented de facto decentralization of the North Korean economy that has been going on in recent decades.
“The method is especially useful in countries with a large agricultural sector, and closed-off dictatorships like North Korea where there isn’t very much information available,” said Ola Hall, one of the researchers.
Since North Korea’s agricultural sector is more dependent on manual labor than many other countries, and has been forced to adapt to frequent fertilizer shortages, increased production has been facilitated by an expansion of farm land rather than sector effectivization. This makes growth more easily observable by satellite.
Agriculture is one of the biggest contributors to the North’s GDP and a major employer for the population.
THE FUTURE OF LUMINOSITY RESEARCH
Up until now, a majority of luminosity-based analysis on North Korea has made use of the DMSP-OLS Stable Lights coverage from the Earth Observation Group, a subunit of the National Oceanic and Atmospheric Administration’s (NOAA) NGDC.
As researchers have pointed out, however, the issue of lacking inter-calibration between satellite sensors under this scheme makes it difficult to compare changes in absolute luminosity over time.
But recently, a new and steadily growing data set is rectifying the issue. Employing a new satellite launched in 2011, the NOAA’s so-called VIIRS scheme (Visible Infrared Imaging Radiometer Suite) collects inter-calibrated data with infrared sensors.
Earth by night, as seen through VIIRS. (NASA Goddard Space Flight Center, via Wikimedia Commons)
“Crucially, the VIIRS sensors are inter-calibrated, so analysts will be confident they are comparing apples to apples, across time and space, in future research,” Pope said.
Commenting on the capabilities of VIIRS data, Christopher Small, a fellow at Columbia University’s Lamont-Doherty Earth Observatory, recently said he knows of only one instance of sensor saturation in the VIIRS product, and that was when the sensor was aimed directly at the spotlight illuminating the Luxor Casino in Las Vegas.
VIIRS imagery, however, is not yet publically available, and accumulating sufficient data to make comparisons over time will take years. Nonetheless, it provides a richer and more nuanced picture than what has previously been available to researchers, Pope said.
Featured image provided by Earth Observation Group, National Geophysical Data Center, NOAA
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