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What can satellite imagery tell us about secondary cities? (Part 2/2)

Sarah Elizabeth Antos's picture
In the previous blog, we discussed how remote sensing techniques could be used to map and inform policymaking in secondary cities, with a practical application in 10 Central American cities. In this post, we dive deeper into the caveats and considerations when replicating these data and methods in their cities.

Can we rely only on satellite? How accurate are these results?

It is standard practice in classification studies (particularly academic ones) to assess accuracy from behind a computer. Analysts traditionally pick a random selection of points and visually inspect the classified output with the raw imagery. However, these maps are meant to be left in the hands of local governments, and not published in academic journals.

So, it’s important to learn how well the resulting maps reflect the reality on the ground.

Having used the algorithm to classify land cover in 10 secondary cities in Central America, we were determined to learn if the buildings identified by the algorithm were in fact ‘industrial’ or ‘residential’. So the team packed their bags for San Isidro, Costa Rica and Santa Ana, El Salvador.

Upon arrival, each city was divided up into 100x100 meter blocks. Focusing primarily on the built-up environment, roughly 50 of those blocks were picked for validation. The image below shows the city of San Isidro with a 2km buffer circling around its central business district. The black boxes represent the validation sites the team visited.
 
Land Cover validation: A sample of 100m blocks that were picked to visit in San Isidro, Costa Rica. At each site, the semi-automated land cover classification map was compared to what the team observed on the ground using laptops and the Waypoint mobile app (available for Android and iOS).

What can satellite imagery tell us about secondary cities? (Part 1/2)

Sarah Elizabeth Antos's picture

The buzz around satellite imagery over the past few years has grown increasingly loud. Google Earth, drones, and microsatellites have grabbed headlines and slashed price tags. Urban planners are increasingly turning to remotely sensed data to better understand their city.

But just because we now have access to a wealth of high resolution images of a city does not mean we suddenly have insight into how that city functions.

The question remains: How can we efficiently transform big data into valuable products that help urban planners?

In an effort a few years ago to map slums, the World Bank adopted an algorithm to create land cover classification layers in large African cities using very high resolution imagery (50cm). Building on the results and lessons learned, the team saw an opportunity in applying these methods to secondary cities in Latin America & the Caribbean (LAC), where data availability challenges were deep and urbanization pressures large. Several Latin American countries including Argentina, Bolivia, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama were faced with questions about the internal structure of secondary cities and had no data on hand to answer such questions.

A limited budget and a tight timeline pushed the team to assess the possibility of using lower resolution images compared to those that had been used for large African cities. Hence, the team embarked in the project to better understand the spatial layout of secondary cities by purchasing 1.5 meter SPOT6/7 imagery and using a semi-automated classification approach to determine what types of land cover could be successfully detected.

Originally developed by Graesser et al 2012 this approach trains (open source) algorithm to leverage both the spectral and texture elements of an image to identify such things as industrial parks, tightly packed small rooftops, vegetation, bare soil etc.

What do the maps look like? The figure below shows the results of a classification in Chinandega, Nicaragua. On the left hand side is the raw imagery and the resulting land cover map (i.e. classified layer) on the right. The land highlighted by purple shows the commercial and industrial buildings, while neighborhoods composed of smaller, possibly lower quality houses are shown in red, and neighborhoods with slightly larger more organized houses have been colored yellow. Lastly, vegetation is shown as green; bare soil, beige; and roads, gray.

Want to explore our maps? Download our data here. Click here for an interactive land cover map of La Ceiba.

Rethinking saving practices in the digital era

Margaret Miller's picture



3-1-0 Three minutes to complete the online loan application, one second for approval and with zero human touch for SME loans. This is the marketing slogan used by Ant Financial, one of China’s largest online lenders with more than 400 million active users.

Digital finance is a cost-effective route to financial inclusion for many unbanked and underserved consumers in emerging markets. But digital finance is also still developing and maturing, with many open questions on the impact it will have. One of the most important of these is whether digital finance will ultimately help consumers to make better financial decisions over time.

October 31 is World Savings Day, a day which emphasizes the importance of savings to economic development, and provides a good occasion to look at how fintech may help solve the challenge of savings.

Gender and sex inequalities in water, sanitation, and hygiene

Libbet Loughnan's picture

This blogpost is part of a series of thematic blogs for the World Bank's Water Supply, Sanitation, and Hygiene (WASH) Poverty Diagnostic.

Woman carries water containers near polluted stream and water pipe in Maputo, Mozambique

Addressing gender and sex inequalities in WASH is not only recognized in Sustainable Development Goals (SDGs) 4 and 6, it is central to the entire ambition of the SDGs themselves. Some water, sanitation, and hygiene issues are faced only by women because of their biological sex, whereas others are more influenced by gendered societal norms. To truly leave no one behind, we need to be mindful of and work against gender and sex inequalities in all development work. 
 
New World Bank research is a valuable contribution to doing just that.  ‘Reducing Inequalities in Water Supply, Sanitation, and Hygiene in the Era of the Sustainable Development Goals’ reveals that a drastic change is required in the way countries manage resources and provide key services, starting with better targeting to ensure they reach those most in need.  In many cases, this means women and girls. 

Weathering storms in Central America: The impact of hurricanes on poverty and the economy

Oscar A. Ishizawa's picture
Countries are facing increasingly frequent negative impacts from adverse natural events. Central America, a region prone and vulnerable to disasters, is a clear example. Just from 1992 to 2011, Central America was hit by nearly 70 hurricanes with an average of 8 events per year, hindering sustainable economic growth.

Between 2005 and 2014, due to natural disasters, the region had a nominal cumulative loss of around US$5.8 billion, and witnessed more than 3,410 deaths and hundreds of thousands of displaced people. More recently, in October 2011, Tropical Depression 12-E hit the coasts of El Salvador and Guatemala with damages amounting to nearly US$1 billion.

In two recent studies, we evaluated the causal impacts of hurricane windstorms on poverty and income as well as economic activity measured using night lights at the regional and country level. In both cases, we applied a fully probabilistic windstorm model developed in-house, and calibrated and adjusted it for Central America. The first study (on poverty) used yearly information at the household level (for income and poverty measures) as well as the national level (GDP per capita). Due to the limited comparable household data between the countries, we decided to follow up with the second study (on economic activity) using granular data at the highest spatial resolution available (i.e., 1 km2) to understand more deeply the (monthly) impact over time.

Our results are striking:

One PPP Program, Two World Bank Group Teams, and the MIT

Bernardo Weaver's picture



The largest Public-Private Partnership deal in Central America was recently highlighted at one of the world’s most prestigious universities during the Massachusetts Institute of Technology’s (MIT) 9th Annual Sustainability Summit. Under this year’s theme, Funding the Future, the event brought together more than 300 participants from students, startup CEOs, academia, think tanks and financial investors.

To promote peace and development, let’s talk about government spending on security and criminal justice

Ede Ijjasz-Vasquez's picture
Governments spend a lot of money to contain violence. In 2015, some $1.7 trillion was spent on defense by governments worldwide . While the primary responsibility for the provision of security and justice services lies with governments, those functions may carry a heavy fiscal burden as they often make up significant portions of national budgets. Yet little work has been undertaken on the composition of security sector budgets, or on the processes by which they are planned and managed.

In an effort to address this issue, the World Bank Group and the United Nations embarked on a three-year partnership that led to the publication of a new report titled Securing Development: Public Finance and the Security Sector. It is a sourcebook providing guidance to governments and development practitioners on how to use a tool called “Public Expenditure Review (PER)” adapted to examine the financing of security and criminal justice institutions.


 

Eradicating household air pollution will pay for itself

Ernesto Sanchez-Triana's picture

© Isabelle Schäfer/World Bank

Globally 2.9 million people died from household air pollution in 2015, caused by cooking over foul, smoky fires from solid fuels such as wood, charcoal, coal, animal dung, and agricultural crop residues. Well over 99% of these deaths were in developing countries, making household air pollution one of their leading health risk factors.

Many women across the world spend their days and evenings cooking with these fuels. They know the fumes are sickening, which is why some cook in a separate outhouse or send the children to play while they cook. Sadly, these small actions cannot fully protect the young. As for the women themselves, they suffer incredible morbidity and mortality from household air pollution.

Managing PPP risks with a new guide on guarantees

Victoria Rigby Delmon's picture



Just two years ago, Ghana was experiencing unstable commodity prices and a deteriorating macroeconomic situation. Yet, through a unique combination of World Bank guarantees nearly $8 billion in private investment was mobilized for the Sankofa Gas Project—the biggest foreign direct investment in Ghana’s history. The transformational project helped address serious energy shortages and put the country on a path to economic growth.
 
This is just one example illustrating how risk mitigation products play out in practice to encourage private sector investment and improve people’s lives.

The Central Matter: An artistic analysis of Central America's Nini subculture

Rafael de Hoyos's picture


On her daily walk down the muddy road that connects her home with school, Beatriz would sing a cumbia and dream of becoming a professional dancer. However, she would soon find out that her aspirations were short lived. At the age of 14, Beatriz got pregnant and never went back to school. In the six years following her pregnancy, she struggled with an unstable and low-paid job, cleaning rich houses in Guatemala City. By the age of 20, without minimum skills and a secure job, Beatriz had little control over her life and a murky picture of her future loomed. 


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