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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.

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. 

Indigenous peoples, forest conservation and climate change: a decade of engagement

Kennan Rapp's picture
Women in Panama participated in activities supported by the capacity building program. Photo credit: World Bank  


This year’s UN Permanent Forum on Indigenous Issues, which kicked off last week in New York, marks the 10th anniversary of the United Nations Declaration on the Rights of Indigenous Peoples.
 
The World Bank’s Forest Carbon Partnership Facility (FCPF) is coming up on its own 10-year anniversary. Since 2008, the FCPF has run a capacity building program for forest-dependent indigenous peoples. The initiative, with a total budget of $11.5 million, has worked to provide forest-dependent indigenous peoples, national civil society organizations, and local communities with information, knowledge and awareness to increase their understanding of efforts to reduce emissions from deforestation and forest degradation (REDD+), and to engage more meaningfully in the implementation of REDD+ activities. The program recently wrapped up its first phase (2008-2016), which included 27 projects, and presented the results at a side event to the Permanent Forum. 

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. 

A Lifetime Approach To Preventing Violence In Latin America

Jorge Familiar's picture
A prevention program against crime and violence in Zacatecoluca, El Salvador, supports sporting activities for the children from this municipality. Photo: Victoria Ojea/World Bank

Prioritizing infrastructure investments: Panama’s long-term path to PPPs

Cledan Mandri-Perrott's picture


In Panama, a healthy economic climate and enthusiastic institutional support provided an ideal testing ground for the World Bank’s Infrastructure Prioritization Framework (IPF). The country’s GDP growth and economic buoyancy in 2014 motivated an ambitious public investment program, accompanied by a high number of infrastructure project proposals to the Ministry of Economics and Finance. Coupled with political commitment to narrow the deficit, Panama moved to implement select projects for a five-year strategic period.

Latin America and the Caribbean: seizing a trillion dollar opportunity in climate investments

Christian Grossmann's picture
 Alessandra Bazan Testino / IFC
Green-bond supported wind farm in Penonome, Panama. Photo credit: Alessandra Bazan Testino / IFC 


First published by Capital Finance International.

Soon the world will celebrate the one-year anniversary of the historic climate agreement signed in Paris in December 2015. The agreement will be implemented through country-led greenhouse gas (GHG) emissions reduction commitments known as their intended Nationally Determined Contributions (NDCs), which to date have been submitted by 189 countries covering 95 percent of global GHG emissions. 
 
Apart from signaling concrete commitments, these reduction targets also offer a clear signpost of the investment direction countries need to follow as the global economy steers towards a low-carbon, climate-resilient pathway. Estimates point to between $57 trillion and $93 trillion in new low-carbon, climate resilient infrastructure investment by 2030.[1] How developing countries evaluate and respond to their infrastructure needs will greatly determine their ability to meet GHG reduction commitments.

Panama Canal expansion: A smart route for boosting infrastructure in Latin America

Philippe H. Le Houérou's picture
Since it opened in 1914, the Panama Canal has been one of the world’s most important trade assets and a marvel of engineering. Its expansion has doubled the canal’s cargo capacity, adding a new lane and bigger locks that will shake up shipping routes and make seaborne trade less costly and more efficient.
 
© Panama Canal Authority


Panama, already projected to be Latin America’s fastest-growing economy over the next five years, was the big winner when the expanded canal opened its locks on June 26. New port projects and related logistics hubs are in the works to attract global manufacturers and further enhance the country’s competitiveness.

Who are the barefoot solar sisters…and how can they help forest communities?

Ellysar Baroudy's picture
Photo credit: Lisa Brunzell / Vi Agroforestry
 
In Kenya, a group of Maasai grandmothers provide an inspiring example of how simple actions can transform societies and how, when empowered, women can break down barriers between men and women.

These women never had the opportunity to attend school. But now aged between 40 and 50 years old, they found themselves with a new task. They received training and were tasked with installing and maintaining solar lighting systems in their villages.
 

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