nominatim

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OpenStreetMap and Nominatim

As Badgers relies on a political structure of the world to determine regions, we relay on OpenStreetmap data via the Nominatim Services.

This is a great free and public service and another sample what open source and crowd sourcing can accomplish. We consume their service but we make sure to play fair, i.e. throttle request frequency, cache the retrieved results etc. Beyond the requirements they state, we also shift some of our requests on less busy times like (European) night and weekend. Beyond friendly consumption Badgers also contributed a little bit back to OSM/Nominatim, mainly in form of data corrections to OSM data and bug reports to Nominatim.

We truly recommend these systems. However there are issues, we have to cope with and I though I mention them here, not to say bad things about OSM and Nominatim, but to document the chances and boundaries of such services. Note that in preliminary experiments Nominatim was more reliable than Google Maps for our purpose.

Issues:

  • Wrong data. The amount of data in OSM is huge, and the quality and speed of contribution varies from region to region, therefore sometimes data is not always correct in time.
  • Wrong data. We've already run in instances of OSM vandalism, i.e. some unbearable people renaming Finland into Alcoholia, an error which propagated into our database.
  • Interface. The machine readable Nominatim API unfortunately occasionally delivers wrong intermediate political structures, which are sometimes historic, sometimes something else and which are not displayed in the human UI. Several Github issues have been filed so far, unfortunately without a general solution.
  • Interface. The Nominatim API does not deliver IDs of found structures forcing us, to work on structure names, which is usually a very bad idea.
  • Interface. As we retrieve Nominatim data on demand, and try to reread fresh data, we really struggle with updates which are too different from the data few weeks ago.
  • Downtimes. Occasionally Nominatim is down.

Considerable programming effort has been gone into making our end of the Nominatim interface robust against above issues, but still there is also continuous manual effort going into this, to keep things tidy. Especially before we establish Ruler or Mapper badges, we have to do some manual work before we establish awards based on bugs. The major part of the queue for this work is roughly summarized on the Suggested Regions page.

  • Last modified: 6 years ago
  • by Frank Nestel