Consider the blank region. Nothingness. Terra Incognita.

It may make you feel uneasy, with strong urges to know this unknown space.

It makes me want to explore and to discover. I want to find out the best parts, and share these places online.

Now consider this same space, under a the cover of a giant polygon. This polygon says the land is defined as a parking lot or perhaps it is a wetland? The OSM notes say that the data comes from a governmental organization of those particular area types. They are the authoritative information source. Do we conclude this map location is finished …?

On one hand, I can see how filling a map with information is a good thing, especially when none exists. But I question the methods used on these massive polygon imports, specifically creating data that appears certainly correct. In contrast, the TIGER data was imported with an expectation that the road data was certainly incorrect. Indeed, my time is spent verifying roads and correcting the street names. A tag was even created verified=no emphasizing the questionable accuracy of the data.

But on my way to survey the TIGER roads, I pass many terrain types that are head-shakingly incorrect. In the OSM database, they appear as a mass import, from some government agency that focuses on that land type. Yes, I understand these geometries can and should be adjusted, but there is no way to know how accurate it is presently. Has it been checked through satellite imagery, does it overlap another terrain type, or has anyone surveyed? None of these things are specified in the polygon tags, so we assume it is correct. Worse, would-be mappers are now discouraged from exploring the area, because it seems to be already defined, so the incorrect data remains unchecked.

I sympathize with mappers who want to cover up all the uncomfortable blank spaces on the map. It drives my OSM involvement, too. But don’t trade incompleteness for inaccuracy.

• Take ownership of the verification of imports.
• Limit the import scope until verification is managable.
• Consider using a node for your area data instead of a polygon.

There is still something beautiful and special about the unexplored places. Let’s not cover it all in polygons.

Public domain image credit: Il designo del discoperto della Nova Franza by Paolo Forlani, ca. 1566