Syndicate content

Argentina

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.

获奖摄影作品捕捉可持续发展城市的未来

Xueman Wang's picture
Also available in: English

可持续城市摄影作品竞赛的出发点很简单。我们想要了解世界各地的人们听到“可持续城市”这个词会“看”到什么。

   

可持续城市全球平台从全球四十多个国收到就九十多张参赛作品,内容发人深省。

摄影师通过照片试图传递的是一种需求:对能使城市恢复能力更强、更加可持续的基础设施的迫切需求,或者追求为所有人建设可持续社区的绿色理想的需求。

今天是世界城市日,是最适合与你们分享本次摄影竞赛十位入围者名单的日子, 这些入围者中包括三位获奖者和一位气候行动荣誉奖获得者。
 
人们几乎可以从Yannick Folly的获奖作品中感受到贝宁城市的混乱和汽车尾气的味道,汽车沿着狭窄的巷子艰难爬行,与摩托车和行人挤在一起。

 

Yanick Folly (贝宁) 获奖者

日复一日的发展,我们的世界一直在变化。看看充满活力的贝宁集市就能感受到这种变化。#SustainableCities

这张照片提醒人们城市是由人组成的。任何建设可持续城市的解决方案对城市居民而言必须是合理的,因为每天行走在城市街道上的人是他们每天。

 

这种渴望在其他作品中也显而易见。

 

尽管很多摄影师来自世界各地的发展中国家,然而,其中相当一部分分享的却是在我们看来的环境友好型城市:新加坡、阿姆斯特丹、伦敦、巴黎等的照片。我们看到了很多发达国家公园的照片,都在传递同一个信息: 这样的绿色空间和人行道正是我们希望城市拥有的。

 

Adedapo Adesemowo(英国/尼日利亚)

现在的奥林匹克公园曾经是石油、沥青、砷和铅的废物倾倒场所 #SustainableCities
很多作品也反映了人们梦寐以求的城市和大部分人实际生活在其中的城市的巨大差别。
 
我们收到了很多可能被许多人归类为“农村地区”的照片,但是我们应该抛开这些偏见:一些发展中国家的“城市”不过是简陋的城镇而已。
 
所以当我们看到来自尼日利亚的Oyewolo Eyitayo的这幅获奖作品时,就更有理由感到兴奋。在你看到一半是土路的路上成排的太阳能板之前,你可能觉得这只是一张典型的平淡无奇的城市郊区的照片。
 
Oyelowo Eyitayo (尼日利亚) – 获奖者
选择太阳能是简单而有效的#气候行动,可以帮助抵御气候变化。#SustainableCities

These winning photos capture the future of sustainable cities

Xueman Wang's picture
Also available in: 中文
The premise behind the Sustainable Cities photo competition was simple. We wanted to learn what people around the world “see” when they hear the words “sustainable cities.”
 
The submissions – and we at the Global Platform for Sustainable Cities received more than 90 entries from over 40 countries around the world – are very revealing.

What the photographers tried to communicate was a need: both the urgent need for infrastructure that leads to more resilient, sustainable cities, or a need to aspire to greener ideals of building sustainable communities for all.

There is no better day than today, World Cities Day, for us to share with you the 10 finalists – including 3 winners and an honorable mention for climate action – of the photo competition.

In the winning photo by Yanick Folly, one can practically feel the chaos of a city in Benin, the smell of exhaust fumes as cars crawl up alongside motorcycles and pedestrians down narrow alleyways.

Yanick Folly (Benin) – Winner
Growing day by day, our world is always moving. Just see the big vibrant Benin market. #SustainableCities

The photo is also a reminder that cities are made of people. Any set of solutions for “sustainable cities” will have to make sense to a city’s inhabitants, who tread its streets daily.
 
In other photos, the aspiration is palpable. 

Many of the photographers are nationals of developing countries from all over the world. Yet quite a few of them shared photos of cities we regard as environmentally friendly: Singapore, Amsterdam, London, and Paris... We saw many photos of parks in developed countries, and heard the same message: These green spaces and pedestrian walkways are what we want in a city.
 
Adedapo Adesemowo (UK / Nigeria)

From a waste dumping ground for oil, tar, arsenic, and lead to an Olympic park. #SustainableCities
Many photos also reflect the vast difference between the aspirational city, and what most people actually live with.
 
We received photos of what many of us may categorize as rural areas, but we should reconsider these preconceptions: some “cities” in developing countries are little more than makeshift towns.
 
So, it is all the more reason why we are excited about this winning photo by Oyewolo Eyitayo from Nigeria. You might think this is an uneventful photograph of a typical urban suburb. Except that the half dirt roads are lined with solar panels.
 
Oyelowo Eyitayo (Nigeria) – Winner
Going solar is a simple & impactful #climateaction that can help combat climate change. #SustainableCities

Urban Indigenous Peoples: the new frontier

Ede Ijjasz-Vasquez's picture
Photo by Victoria Ojea / World Bank
Photo: Victoria Ojea / World Bank

Invited to think of Buenos Aires, most would probably think of elegant cafés, beautiful architecture, passionate football fans, and buzzing streets. Invited to think harder, you might also think of its villas (slums), street children, and other less gleeful views. But no matter how hard you try, very few would associate Buenos Aires with Indigenous Peoples. Yet, Buenos Aires has the largest concentration of indigenous populations in Argentina, which is itself rarely associated with Indigenous Peoples, but has the seventh largest indigenous population in Latin America (close to one million). In effect, over 40 indigenous communities are officially registered in urban areas of the Buenos Aires Province, and as much as one quarter of all Indigenous Peoples in Argentina make a living in or around the Capital of Tango, whether in communities or not.

What do they do? What conditions they are living in? What is happening to their unique cultures and languages? Are they losing connection with their ancestral lands? Is the special legislation protecting their collective rights relevant in the cityscape? In sum, how is the city changing them and, inversely, how are they shaping the urban landscape? These and other questions were at the heart of the dialogue I had with graduate students from across the Latin America region in FLACSO – University of Buenos Aires, last week, on the occasion of the presentation of the report Indigenous Latin America in the Twenty-First Century, in Buenos Aires.

The “human scale” in public urban areas

Judy Zheng Jia's picture

Slideshow: Reimagining a park, a river, and other public spaces in Seoul (Photos by Judy Zheng Jia / World Bank)

"If you lose the human scale, the city becomes an ugly place," said Joan Clos, Executive Director of the UN-HABITAT at the Habitat III Conference last month. But more than being "ugly," the lack of good public urban spaces, such as open spaces, parks, and public buildings, often contribute to low livability in many of the world's congested and polluted cities. In fact, the importance of the issue received recognition in SDG 11, Target 7, which calls for the provision of “universal access to safe, inclusive and accessible, green, and public spaces, in particular for women and children, older persons, and persons with disabilities,” by 2030.
 
Global experience shows that disconnected, underutilized areas in urban settings can, instead, be opened up to a variety of uses to allow for improved social inclusion, social mixing, civic participation, recreation, safety, and a sense of belonging, ultimately contributing to urban prosperity. Well-designed and well-managed public spaces also offer benefits to environmental sustainability, transport efficiency, and public health improvements, and can equally serve women, the disabled, and people of all ages.

The importance of good urban spaces was the topic of an international workshop—“Vitalizing Cities with Public Space”—held in Seoul on November 14-17, 2016 and co-hosted by the Korea Research Institute of Human Settlements and the World Bank’s Urbanscapes Group. Eight cities from around the world—Seoul, Singapore, Buenos Aires, Chongqing, Kakamega, Zanzibar, Astana, and Tashkent—participated to discuss challenges and opportunities for better urban planning and design.

What if…we could help cities more effectively plan a lower-carbon future?

Stephen Hammer's picture
Visit worldbank.org/curb

If climate change were a jigsaw puzzle, cities would be a key piece right at the center of it. This was reinforced by more than 100 countries worldwide, which highlighted cities as a critical element of their greenhouse gas (GHG) emission reduction strategies in their national climate plans (aka INDCs) submitted to the UNFCCC in 2015.

Since the ensuing signing of the Paris Agreement, these countries have shifted gear to focus on turning their climate plans into actions. What if, as many of us may wonder, we could find a cost-effective and efficient way to help put cities—in developing and developed countries alike—onto a low-carbon path of growth?

CURB: Climate Action for Urban Sustainability, launched this Climate Week, is an attempt to do just that. A free, data-driven scenario planning tool, CURB can readily help cities identify and prioritize climate actions to reduce carbon emissions, improve overall efficiency, and boost jobs and livelihoods.

A joint vision for effective city planning

What CURB can do for cities owes very much to the inspiration and stories we have taken from them in developing the tool. It was a fortuitous few hours in early 2014 at the C40 Cities Climate Leadership Summit in Johannesburg, South Africa that really got the ball rolling on the development of CURB.

Five reasons cities should take a leading role on food waste

John Morton's picture
Reported figures from the Food and Agriculture Organization of the United Nations (FAO) on food loss and food waste highlight its importance to the global environment. Food loss and waste annually contribute 3.3 gigagrams of CO2 equivalent, or over twice the total emissions of India; waste 250 cubic kilometers of water which is equivalent to 100 million Olympic-sized swimming pools; and 1.4 billion hectares of agricultural land, an area larger than China. Considering that, if only 1/4 of the food lost or wasted across the globe could be recovered, it could feed 750 million people, it is also shocking when presented in the context of global food insecurity and hunger.
 
These statistics highlight the need to address the problem as global citizens. But if you look at it closer, the incentives for action are indeed very local, making cities—as the centers of consumption in the world—important game changers with strong reasons to take action.

How Latin America’s housing policies are changing the lives of urban families

Luis Triveno's picture
Photo: Pierre-Yves Babelon/Shutterstock
In an effort to harness the benefits of urbanization and improve the living conditions of the urban poor, Latin American countries have experimented with housing subsidies. Now that the region has several decades of experience under its belt, it is time to look back and ask: Have subsidies worked? What kind of impact have they had on the lives of lower-income residents? Moving forward, how can cities pay for ongoing urban renewal?

To address those questions and share their experiences, officials in charge of designing and implementing national housing policies in eight countries (Argentina, Bolivia, Brazil, Chile, Colombia, Mexico, Paraguay, and Peru) recently met in Washington DC, along with representatives from the World Bank, Cities Alliance, the Urban Institute, and Wharton's International Housing Finance Program.