Hidden messages in OpenStreetMap


Reviewing OpenStreetMap data processed to generate visualizations of builtup areas i noticed some peculiar structures in northern India. Here how this looks like:

These are the result of selective mapping in OpenStreetMap – some mapper has mapped settlements along a circular path but not elsewhere.

Historically it is not that uncommon in OpenStreetMap to have abstract and artificial structures hidden in data otherwise accurately representing the actual geography. One particularly popular method of doing this is by doing imports or automated edits in a certain sequence – the most notable case being the famous ban potlatch! message:

This kind of hidden message however only shows up in more detailed analysis of the data. The circle above is also visible in the normal map.

And since mappers in OpenStreetMap is allowed to freely choose what they map and what they don’t map the only way to remove this kind of hidden message without destroying useful data is to map the rest of the area with at least the same level of detail and accuracy.

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