During the 20th Century, aerial surveys captured hundreds of millions of high-resolution photographs of the Earth’s surface. These images, the precursors to modern satellite imagery, represent an extraordinary visual record of the environmental and social upheavals of the 20th Century. However, most of these images currently languish in physical archives where retrieval is difficult and costly. Digitization could revolutionize access, but manual scanning is slow and expensive. Automated scanning could make at-scale digitization feasible, unlocking this visual record of the 20th Century for the digital era. Here, we describe and validate a novel robot-assisted pipeline that increases worker productivity in scanning 30-fold, applied at scale to digitize an archive of 1.7 million historical aerial photographs from 65 countries.

We introduce SPLAT (Stitching Pipeline for Large Aerial Tilesets), a new method for the automated and simultaneous stitching and geolocation of large archives of aerial historical photographs. Millions of physical prints and films of aerial images are archived around the world. The growing share of these images being digitally scanned motivates the development of a robust, scalable, and efficient method to process them and make them suitable for quantitative analysis. Existing solutions can stitch datasets comprising hundreds of historical images, either using time-consuming manual geolocation and tie point collection or, alternatively, automated techniques in those cases where extensive and detailed metadata is available.To our knowledge, SPLAT is the first pipeline to be able to process millions of images. It can do so by using a simplified model for the reconstruction of the image positions, making use of available metadata, and optimizing the amount of manual labor involved in the process.We apply SPLAT to a dataset of 1.67 million images from the National Collection of Aerial Photography (NCAP) in Scotland, which includes coverage of numerous countries, including former British colonies, between the 1940s and 1980s. We report the results of SPLAT on a selected group of African countries. We show we are able to geolocate and retrieve footprints for more than 50,000 images. An analysis of the goereferencing error on a set of evaluation ground control points yields a median (mean) error of 76 (197) meters on the prediciton of their location.

Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.

Existing strategies for improving global access to safe drinking water have met only limited success. We consider an unglamorous and often neglected dimension of drinking water infrastructure provision: cleaning. We randomly assigned caretakers of community wells to participate in a training workshop about how to clean wells. Thirteen to seventeen months later, wells with caretakers assigned to receive training have negligible rates of contamination with Escherichia coli (13 months: 2%; 17 months: 4%), while control wells have substantial rates of E. coli contamination (13 months: 14%; 17 months: 19%). Rates of contamination with any coliform bacteria are almost halved (13 months: control 55%, treated 30%; 17 months: control 77%, treated 46%). We estimate the cost of preventing exposure to coliform bacteria in drinking water to be US$0.89 per person and that, if scaled up, each US$2376 spent on the intervention could avoid the death of a child.

Access to safe drinking water in rural Bangladesh remains a perpetual challenge. Most households are exposed to either arsenic or faecal bacteria in their primary source of drinking water, usually a tubewell. Improving tubewell cleaning and maintenance practices might reduce exposure to faecal contamination at a potentially low cost, but whether current cleaning and maintenance practices are effective remains uncertain, as does the extent to which best practice approaches might improve water quality. We used a randomized experiment to evaluate how effectively three approaches to cleaning a tubewell improved water quality, measured by total coliforms and E. coli. The three approaches comprise the caretaker's usual standard of care and two best-practice approaches. One best-practice approach, disinfecting the well with a weak chlorine solution, consistently improved water quality. However, when caretakers cleaned the wells themselves, they followed few of the steps involved in the best-practice approaches, and water quality declined rather than improved, although the estimated declines are not consistently statistically significant. The results suggest that, while improvements to cleaning and maintenance practices might help reduce exposure to faecal contamination in drinking water in rural Bangladesh, achieving widespread adoption of more effective practices would require significant behavioural change.

Can transparency interventions improve WASH service provision? We use a randomized experiment to evaluate the impacts of a transparency intervention, a deliberative multi-stakeholder workshop initiated with a community scorecard exercise, in schools in rural Bangladesh. To measure impacts, we combine survey data, direct observations, and administrative data. The intervention leads to moderate but consistent improvements in knowledge of WASH standards and practices, and institutions for WASH service management, but does not improve school WASH service provision or change WASH facility use patterns. Drawing on rich descriptive data, we suggest several reasons why the intervention we evaluate did not improve WASH service outcomes and propose ways to improve the design of future interventions.

Health, and in turn income and welfare, depend on access to safe drinking water. Although the majority of rural households worldwide obtain drinking water from community water sources, there is limited evidence about how effectively these sources provide safe drinking water. This study combines a randomized experiment with water quality testing to evaluate the impact of a program that provides community deep tubewells in rural Bangladesh. The program reduces exposure to arsenic, a major natural pollutant, but not fecal contamination. Households may use fewer sources with fecal contamination, but any such effects are offset by recontamination through transport and possibly storage. The results suggest that while community deep-tubewell construction programs may reduce exposure to arsenic in Bangladesh, reducing exposure to fecal contamination may require interventions that go beyond community sources.

Most development practitioners would list engaging communities in the provision of public services among best practices for improving access. However, whether community participation enhances provision and use of public services relative to a non-participatory approach is largely unknown because few studies compare impacts when the same public service intervention is implemented with and without community participation. This field experiment compares three approaches to providing safe water in rural Bangladesh. Delegating decisions to the community increases use of safe water by about 80% relative to a top-down provider making the same decisions but only when the approach to delegating decisions limits elite influence.

Does better population health lead to growth in per capita income? Theory is ambiguous and empirical evidence is very limited. In 2001, a steep fall in antiretroviral (ARV) drug prices triggered rapid and massive expansion of ARV therapy coverage in lower-income countries. Exploiting the sharp resultant changes in population health, I show that ARV therapy coverage expansion led to growth in GDP per capita. The positive effects on growth most likely persist for around four years. ARV therapy coverage expansion could explain around a third of the sub-Saharan African growth miracle.