Meeting the Demand for Data on Urban Areas

According to the United Nations, the world’s urban population has grown rapidly in the past 75 years, increasing from 751 million in 1950 to 4.2 billion in 2018. This growth is driven by an overall increase in the world’s population coupled with a rise in the percentage of people living in urban areas. Together, these two factors are projected to add 2.5 billion to the world’s urban population by 2050, with almost 90 percent of this growth happening in Asian and African cities alone.

These are eye-opening statistics. It is critical for state and local officials, humanitarian organizations, researchers, and others involved with environmental sustainability, public health, and hazard resilience to have accurate fine-scale data on the location, population, and spatial extent of human settlements, as well as an understanding of their vulnerability and assets to mitigate climate impacts.

To help decision makers and researchers stay abreast of urban population and environmental characteristics, NASA's Socioeconomic Data and Applications Center (SEDAC) has released a collection of 12 datasets focused on different aspects of the urban environment, such as air quality, extreme heat exposure, population size and location, and progress on sustainable development goals. 

The datasets include:

Meeting the Demand for Data on Urban Centers

For SEDAC Project Scientist and Columbia University’s Center for Integrated Earth System Information (CIESIN) Research Scientist Susana Adamo, the presentation of these datasets as a collection is significant, as it showcases “The concept of urban and the notion that there are many layers to city life, as the datasets in this collection point to different ways of thinking about urban environments.”

The collection provides a way for SEDAC to meet the needs of users investigating the attributes and impacts of urban centers, and on urban centers, around the globe.

“There is a demand among users for information on urban centers and on how urbanization impacts natural systems, but a lot of existing datasets are region or country specific,” said CIESIN Senior Research Staff Assistant Juan Martinez. “The datasets in this collection provide that information for urban areas and most have global coverage.” 

In addition, there are datasets in this collection that provide fine-scale (i.e., 100x100m grid resolution) data that decision-makers can apply at the local level.

“Traditionally we’ve had a lot of 1-kilometer grid cell outputs, which don’t give you a whole lot of variation inside of a settlement. There is a push across all data producers, including in SEDAC, to get at that finer scale to make data a little bit more translatable,” said Dana Thomson, CIESIN’s Associate Director for Science Applications. Forthcoming data products in SEDAC’s urban collection will be presented by “city segments, which is just kind of a step up from city block, something similar to a United States census track, and that supports decision-making at the local level.”

This combination of global coverage and finer scale data allows SEDAC to engage different types of users, including enterprise users who are interested in national or international trends, such as progress on sustainable development goals, and so-called last-mile users, whose focus lies at the city or sub-city level.   

“A lot of the enterprise users apply datasets in the urban collection [as] baseline datasets… or as a model input,” Martinez said. “But we also have datasets that are more for the last-mile users, who want data that is ready to use at the local level. The datasets in the urban collection can be used by both these user types because we’re providing these data at a global scale. So, if a user has data specific to their local project, they can pair it with a subset of the data they grab from us and move forward.” 

Investigating the Health and Well-Being of Urban Populations

Given the range of topics they cover and their suitability for different types of users, it's clear that the datasets in SEDAC's urban collection have a variety of applications. In a recent NASA Earthdata webinar, “The Many Layers of City Life: Urban Datasets from NASA's SEDAC,” which in addition to introducing the datasets in SEDAC’s urban collection, showed how researchers are using the datasets in this collection. Some publications cited include:

• Decarbonization, population disruption and resource Inventories in the global energy transition, which used the GHS-SMOD and GRUMP datasets to evaluate the impacts of decarbonization strategies on local populations
• Estimating population and urban areas at risk of coastal hazards, 1990–2015: how data choices matter, which used the GHS-POP, GHS-SMOD, dLIGHT, and GRUMP datasets to update estimates of populations in the low-elevation coastal zones (i.e., areas at heightened risk from sea level rise)
• Extreme Humid-Heat Exposure and Mortality Among Patients Receiving Dialysis, which used the UHE-Daily dataset to characterize the association of extreme heat events and the risk of death among patients receiving dialysis in the United States

For Martinez and Adamo, these publications are noteworthy because, in addition to using SEDAC data, they provide examples of how the synthesis of Earth science and socioeconomic data can be used to provide actionable information to decision-makers working to address real-world concerns.

Forthcoming Urban Datasets

In addition to the 12 datasets listed above, SEDAC will add two new datasets to the urban collection later this year that provide information about the environmental risks and vulnerabilities within cities and identify slums, informal settlements, or less-accessible areas inside larger urban areas.

The first is a collection of City and Sub-City Datasets on Urban Climate Vulnerability and Risk that will classify environmental vulnerability and risks for 11,422 cities in 2025 Global Human Settlement Layer Urban Centers Database. This dataset will include characteristics for each city (e.g., location, population density, etc.), information on current environmental vulnerabilities, and future climate risks. The sub-city data will feature 500x500-meter grids with high-resolution environmental variables and classifications, environmental vulnerability (current and future), and include more granular data (e.g., percentage of population at risk, vulnerability ratings).

The second is a Socioeconomic Vulnerability in City Segments dataset that will allow users to identify city segments with high population density and limited road connectivity to the rest of the city based on open-source, global data. This dataset can support the monitoring of SDG 11.1.1 by calculating a proxy for the percentage of urban populations living in slums, informal settlements, or inadequate housing.

For Dana Thomson, the addition of these fine-scale data will be a significant complement to SEDAC’s collection of urban datasets. 

“Ninety percent of the people being added to the planet through 2050 are going to live in African and Asian cities alone, and an overwhelming majority will probably live in the poorest areas of those cities, and we have no maps. We have no way of knowing where those slums are,” she said. “But this isn’t just about slum mapping. It really provides a way of thinking about all of the characteristics that define urban poverty and the expressions of poverty in different contexts.” 

These datasets, in conjunction with the 12 aforementioned datasets in the urban collection, also demonstrate how SEDAC’s work supports NASA’s Earth Science to Action initiative, which aims to provide the data, models, resources, and tools required to help decision and policy makers around the globe implement science-based actions on behalf of their communities.

“A lot of NASA’s [Distributed Active Archive Centers] (DAACs) receive foundational data directly from satellites or other instruments and process them into useful datasets, so most [DAACs] are working on this foundational knowledge level,” Thomson said. “SEDAC really sits at the next level of integrating datasets, making sense of things, translating indicators into something that's interpretable by decision-makers and real people on the ground in communities and cities.”

Data Access

NASA Earthdata Search

SEDAC Data Access and Tools