[Talk-us] administrative boundaries and Nominatim

Serge Wroclawski emacsen at gmail.com
Mon Jul 30 17:05:43 BST 2012


On Mon, Jul 30, 2012 at 8:25 AM, Metcalf, Calvin (DOT)
<calvin.metcalf at state.ma.us> wrote:
> So I'm somewhat confused about how nominatim actually works. A good example is the building I work in (10 park plaza Boston ma) the version of nominitum on the website gets the correct location on the first try (note mapquest has it as the 3rd result) but they have it as being

Often what happens is that you have one of two problems, in this order:

1. Nodes

2. Incorrectly prominent areas

Nodes are a major problem. In the case of a node area, Nominatim will
attempt to guess at how large/prominent the area is. If it's a city,
for example, it will be very lose about how far out it thinks the city
borders are. Neighborhoods, same thing, and so you get these odd
classifications.

The solution to this is to replace nodes with polygons, period.

Often related  is the fact that these nodes are often labeled
incorrectly, or the area nearby is. That's why much of Washington, DC
is considered part of Fairfax, VA, because Fairfax is a node, and a
city.

- Serge



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