Monday, October 15, 2018

On the road

This blog and my Twitter will be less active in the next few days.

I'm on my way to California to have a few weeks off from work and celebrate. My partner completed her masters degree and I finished my PhD, so that's a good enough reason for us to celebrate. See you next month. 

ps. If you really have nothing else better to read in the meantime, have a look at this wonderful  PhD thesis.


image credit: ?, via @CityDescriber (funny bot by Geoff Boing)

Tuesday, October 9, 2018

Friday, October 5, 2018

How Democracies Die

Here is a great seminar by Steven Levitsky talking about his recent book on how democracies die. I cannot emphasize enough the importance of his message in times of strong political polarization like these.

ps. I know. Politics is not really the focus of this blog. However, the coming Brazilian elections (this weekend) are quite depressing and I've found this video very helpful to make sense of the mess we're in. Spoiler alert: the video will not cheer you up.



Thanks Daniel Cardinali for recommending me the video.

Thursday, October 4, 2018

Monday, October 1, 2018

How complete is OpenStreetMap data coverage?

Mikel Maron (MapBox) has addressed this question in 2015 using the CIA World Factbook as a reference. The coverage varies from country to country, as expected, but it's pretty good overall and it only gets better with time. You can check the results for your country here.

More recently, Barrington-Leigh and Millard-Ball addressed the same questions with different methods (ht Ralph Straumann). The authors arrived at a similar conclusion but they also draw some other interesting findings (see the abstract below).  Obs. I'm curious to know why Bolivia stands out from Latin America.

Barrington-Leigh, C., & Millard-Ball, A. (2017). The world’s user-generated road map is more than 80% complete. PloS one, 12(8), e0180698.
Abstract:
OpenStreetMap, a crowdsourced geographic database, provides the only global-level, openly licensed source of geospatial road data, and the only national-level source in many countries. However, researchers, policy makers, and citizens who want to make use of OpenStreetMap (OSM) have little information about whether it can be relied upon in a particular geographic setting. In this paper, we use two complementary, independent methods to assess the completeness of OSM road data in each country in the world. First, we undertake a visual assessment of OSM data against satellite imagery, which provides the input for estimates based on a multilevel regression and poststratification model. Second, we fit sigmoid curves to the cumulative length of contributions, and use them to estimate the saturation level for each country. Both techniques may have more general use for assessing the development and saturation of crowd-sourced data. Our results show that in many places, researchers and policymakers can rely on the completeness of OSM, or will soon be able to do so. We find (i) that globally, OSM is ∼83% complete, and more than 40% of countries—including several in the developing world—have a fully mapped street network; (ii) that well-governed countries with good Internet access tend to be more complete, and that completeness has a U-shaped relationship with population density—both sparsely populated areas and dense cities are the best mapped; and (iii) that existing global datasets used by the World Bank undercount roads by more than 30%.

Completeness of the OSM dataset, by grid cell, January 2016.

credit: Barrington-Leigh & Millard-Ball (2017)


Sunday, September 30, 2018

Quote of the Day - social science

“We live in an era of social science, and have become accustomed to understanding the social world in terms of 'forces,' 'pressures', 'processes', and 'developments'. It is easy to forget that those 'forces' are statistical summaries of the deeds of millions of men and women who act on their beliefs in pursuit of their desires. The habit of submerging the individual into abstractions can lead not only to bad science (it’s not as if the 'social forces' obeyed Newton’s laws) but to dehumanization" (Steven Pinker)

Sunday, September 23, 2018

The day I became a Doctor

I'm very glad  and relieved  to share the news that I became a doctor last week! It might take some time for the university to publish my PhD thesis, so I've decided to make the preprint of the thesis available for download here. I've also created a GitHub repository to share the R code used in the data wrangling, mapping and analysis in the thesis.

My examiners were Nihan Akyelken and Bert van Wee. They were super kind but very challenging, nonetheless. In the end, the PhD viva lasted for 2.5 hours and I was super nervous the whole time. I really enjoyed the viva, though, and I was so surprised when they said I had passed with no corrections that I almost jumped out of my chair. I got this result largely because of my incredibly  demanding  tireless supervisors Tim Schwanen and David Banister, to whom I'm extremely grateful.  All in all, I'm feeling incredibly happy and thankful for the whole journey and the support I received along the away from my family, friends and supervisors. It’s been a truly wonderful and humbling experience.

ps. I still have two papers of the thesis currently under review, but finishing the PhD means that now I'll have much more time to  procrastinate  work on new projects and some others that were put on hold.

photos by my lovely wife, Fabiana - also known as my third supervisor :)

Friday, September 14, 2018

Biographical note: back to the library

Working from the Oxford Bodleian Library and the Radcliffe Camera these days. Getting ready to my PhD defence and the seminar at UCL next week. The blog has been less active these days but I hope to post some good news in the coming days.


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