[Tagging] Tagging of topographic areas with a name

Yuri D'Elia wavexx at users.sourceforge.net
Tue Aug 6 17:25:40 UTC 2013


On 08/06/2013 07:04 PM, Martin Koppenhoefer wrote:
> For other areas other data types might be more adequate:
> Some years ago on the German ML there was this interesting idea to define
> (fuzzy) areas (e.g. lower scale topographic regions like "the European
> Alps"). You put existing objects (like nodes, ways or relations) into a
> relation with the roles inside or outside and some algorithm would
> calculate an area that includes all inside and excludes all outside
> objects. You won't have to be very precise with this, as this kind of rough
> information is only required on lower scales where some kilometers more or
> less won't change anything, just a few nodes should suffice to define
> something as huge as the Alps, and you could reuse (preferably simple and
> stable like peak-nodes) existing geometry.

The message from fly, about about boundary=topologic/geographic though
would solve nicely valleys, mountain groups _and_ other topographic
features under a single umbrella, and it's quite easy to achieve.

to fly: Is this some form of official proposal?

Calculating a concave hull from points, especially where you have nested
geometry is very messy process (I used to do it as a gis developer in
the past). I wouldn't really expect "decent" results even for name
placement.

> +1, usually you will have a river or stream there, as it is the locally
> lowest point (i.e. the needed geometry is already there). An argument
> against reusing rivers to define mountain groups is that they often add a
> lot of complexity and you'd usually not need the borders of a mountain
> group with the precision this allows for (adding relations augments
> complexity and raises the barrier for other mappers to edit).

Ridges can also be quite complex. Also, many times they end way before
the end of the end of the hill or do not exist at all (flat top
mountains). Just to say that the geometry might not always be there.

Also, is there a tagging scheme for the lowest point/depression of a
valley? (I was looking for it recently).





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