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Sustainable Communities

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.

Swallowed by the Sea…Where coastal infrastructure and jobs meet climate change

Karin Erika Kemper's picture


Life is shifting fast for coastal communities in West Africa. In some areas, coastlines are eroding as much as 10 meters per year. Stronger storms and rising seas are wiping out homes, roads and buildings that have served as landmarks for generations.

I was recently in West Africa to witness the effects of coastal erosion. To understand what’s going on, we took a three-country road trip, traveling from Benin’s capital Cotonou, along the coast to Lomé in Togo and then to Keta and Accra in Ghana. These three countries, among the hardest hit by coastal erosion, offer a snapshot of what is happening along the rest of the coast, from Mauritania, via Senegal to Nigeria. 

Girls’ education and the future of a nation

Sri Mulyani Indrawati's picture
School girls in Berastagi, North Sumatra, Indonesia. © Axel Drainville via CreativeCommons
School girls in Berastagi, North Sumatra, Indonesia. © Axel Drainville via Creative Commons

In 1978, we both started our high school education in our home city of Semarang. Our alma mater is located on a major artery in the heart of the city, and occupies a beautiful Dutch colonial building. The robustness of its architecture befits the reputation of our school at that time: a school led by a passionate principal who promoted discipline and effective learning.

In our school, every boy and girl had an equal opportunity to learn and thrive. This is something Raden Ajeng Kartini –national heroine and a pioneer for girls and women’s rights in Indonesia– had fought for. The school was fully equipped with labs for chemistry, physics, biology, and foreign languages. We were fortunate to have the opportunity to receive quality education at one of the best public schools in Semarang. Our school also fared well at the provincial and national level. 

The Internet of Things – from hype to reality

Prasanna Lal Das's picture
DOWNLOAD THE REPORT HERE

Sensors in elevators that alert government agencies to public safety risks; data from school bags to keep children safe; garbage trucks with the smarts to save cities money… The Internet of Things (IoT) will change everything. That is the conventional wisdom. We set out to look for evidence of this change in the government. How fast is it coming? Is it real? And our findings were mixed – sobering, but also encouraging.

On the plus side, we found government agencies keen to apply IoT to improve their business environment or reduce the burden on businesses while simultaneously increasing compliance. On the downside, very few IoT initiatives have been scaled beyond pilots, the business models to sustain IoT infrastructure are under-developed, and the policy landscape is woefully inadequate. There’s significant potential but it requires systematic, informed work by the government, private sector, and civil society.

Helping Brazil realize its infrastructure promise

Paul Procee's picture


Photo: LWYang | Flickr Creative Commons

Since the 1980s, investment in Brazil’s infrastructure has declined from 5% to a little above 2% of the country’s Gross Domestic Product (GDP), scarcely enough to cover depreciation and far below that of most middle-income countries (see figure below). The result is a substantial infrastructure gap. Over the same period, Brazil has struggled with stagnant productivity growth. The poor status of infrastructure is broadly believed to be a key reason for Brazil’s growth malaise.

Trinidad from space: using satellite imagery for better urban management

Ana I. Aguilera's picture
Foto aérea de Trinidad, Bolivia. / Banco Mundial.

The first time I heard of the Bolivian city of Trinidad was exactly 11 months ago. Although Trinidad is the 10th largest city in Bolivia, I confess I did not know much about it. The Ministry of Development Planning (MPD) had commissioned the World Bank a study on intermediate cities in Bolivia, and in my early research I learned that this was a colonial city founded in 1686 during Jesuitic Missions. Similar in its architecture and climate to the southeastern cities of my native Venezuela, Trinidad is extremely vulnerable to flooding that affect thousands of families and businesses each year.

Ranking the world’s megacities is a wake-up call for women’s rights

Monique Villa's picture
Cities are becoming monsters. Look at the world’s biggest megacities. 38 million people live in Tokyo! Try to take a taxi and find the house of a friend in Japan’s capital. You need luck. Six billion people will live in cities by 2045.

Cities are the new states; today, many of the world’s 31 megacities have larger populations and economies than individual nations.

For many people, these big urban centers represent the land of opportunity, offering better chances of employment, increased access to education and health services, social mobility.  For many others it’s a daily struggle for survival. In all big cities, the inequality between rich and poor has become gigantic and the divide seems only to grow.

We conducted a poll to investigate one aspect: how do women perceive their life in the world’s megacities? We chose women because they are the real economic accelerators, re-investing 90% of their salary into their families. When a woman thrives, her immediate community thrives with her.

Throughout June and July, we asked 380 gender experts in the 19 countries hosting the world’s biggest megacities to identify in which they thought women fared best and worst. The findings were eye-opening. They returned a truly compelling snapshot of the wider issues faced by women: from sexual violence, to security, to access to reproductive rights, from the risks of harmful cultural practices, to the lack of access to economic opportunities.

London was voted the world’s most female-friendly metropolis, thanks to its provision of free healthcare and access to economic resources such as education and financial services.  Tokyo and Paris came second and third.

But when we look at what concerned women most, the poll offers proper food for thought. In London, for example, experts cited the gender pay gap (a recent study by the Chartered Management Institute and XpertHR found on average, women earned £12,000 less than their male counterparts, while just 26% of director-led roles are filled by women as opposed to 74% by men) as well as extortionate childcare costs, as two of the major issues facing women today.
 

Project monitoring in fragile places does not have to be expensive

Andre Marie Taptue's picture



Conflict and violence are shrinking the space for development at a time when donors are scaling up their presence. To reconcile the conflicting objectives of staff safety with a need to do more (or a greater volume of investment), and doing it better (through higher quality projects), many development workers have started to rely on third party monitoring by outside agents, an approach that is costly and not always effective.
The case of Mali demonstrates that alternatives exist.

Less than a decade ago Bank staff could travel freely around in Mali, even to the most remote communities in the country. But today, a mix of terrorism and armed violence renders field supervision of projects impossible in many locations.

To address this challenge—and in the wake of the 2013/14 security crisis in northern Mali—a monitoring system was designed that is light, low cost, and suited for monitoring in insecure areas, but also problem oriented and able to facilitate improvements in project implementation.

Can blockchain help us better assist refugees and migrants in transit? Innovative Financing for Development

Kristina Mikulova's picture
Technology can both empower and disempower. At a recent workshop on blockchain, we landed a challenge: how can we use it to facilitate refugee integration?

I am an immediate misfit in the dynamic multiverse of people speaking in code. But at this USAID event led by the UNDP Alternative Finance Lab and AID:Tech, I wasn’t the only one.


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