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)