I just published a study on the OSM buildings geometry for 12 cities, providing indicators and visualisations to help monitor the OSM data in these cities. See https://twitter.com/pierzen/status/1034529503740080128 https://opendatalabrdc.github.io/Blog/#!Database_Quality_Analysis_Building_overlaps_and_irregular_geometries_Various_cartographic_projects_comparison.md This is part of OpenDataLabRDC initiated by OSM-RDC and Potentiel 3.0 with the objective to share with other communities to enhance the OSM database.
Some would say that there are a lot more indicators in Quality tools such as Osmose, KeepRight and OSM Inspector. Our approach is to provide indicators to monitor a territory and the Map visualisations to highlight quality problems. It would be great if we could have global indicators for an area coming out of these tools. The number of contributors is limited in Africa and the risk is that errors created by mapathons while participating to Crisis responses stay has is for years. The buildings geometry and overlaps are problems that are often mentionned. Our approach is to identify buildings traced with irregular forms to examine if they correspond to the real architecture of buildings or in fact are imprecise tracing of buildings. Various factors can contribute to that such as lack of details / inprecise imagery for an area, dense urban or unplanned urbanisation areas, or simply participation of new contributors to various Tasking manager projects without sufficient training and control of data quality by the organizers. Quite surprisingly, the ratio of Irregular buildings vs Total buildings for an area vary a lot, from 1.6% in Kisenso, Kinshasa (DR Congo) to 72.4% in Victoria, Seychelles. Fo Building overlap errors, we see it varying from 0.2% in Accra to 24% in Pointe-Noire, Congo-Brazzaville. In fact, the tasking manager instances are good to distribute tasks among a great number of simultaneous participants, but for monitoring, management of mapathons in particular, we need to find solutions that assure a better OSM quality. Note that Kinshasa in DR Congo is part of the 12 african cities who started recently their participation to Open Cities Africa. This project is part of the World Bank’s Global Facility for Disaster Reduction and Recovery (GFDRR) program. Pierre
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