[OSM-dev] (no subject)

Roland Olbricht roland.olbricht at gmx.de
Mon Jun 15 17:11:37 BST 2009


Hello everybody,

Wolfgang has written
> and why ("an area is a closed way with some tag attached"
> simply doesn't cut it).
>
> Or, in case that was still not concrete enough: in Austria alone, there
> are
> currently on the order of 750 geometries that are perfectly valid in osm
> but
> not digestible by quite a few GIS-enabled databases

Well, just take it from a mathematical point of view. One can define any area by providing its border. A point is inside if and only if it is separated by the south pole by an odd number of borders. I you need a mathematical proof, I'll put one on the wiki.

So there is no need to bother the mappers with any "outer", "inner" tag, order on relation members or whatever. The only thing needed would be a tag to reverse the area to make areas possible that cover the south pole. The last thing I would think about is to bully the community with another bot that changes what a poorly designed application fails to read.

There are at the moment more than 44,000 valid areas in the planet data ("multipoygon"s and administrative units). There are a lot of tools that can digest this data. The interpretation of this data would need neither a relevant amout of code nor computation time. Feel free to ask for sample code. So if a certain database or tool fails on mathematical facts, I would have doubts about that database resp. tool, not about OSM.

Cheers,
Roland

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