[Tagging] natural=bay as nodes are evil

[moltonel 3x Combo]

On 27/10/2014, Christoph Hormann <chris_hormann at gmx.de> wrote:
> On Monday 27 October 2014, Janko Mihelić wrote:
>>
>> Reverse geocoding. A boat comes to a bay, captain looks on a screen,
>> and it says "You are in Guantanamo Bay".
>
> But this is exactly what does not work with a hand mapped polygon either
> since the edge of the bay is not well defined.
>
> It seems to me the desire to have bays mapped as polygons here stems
> from the desire to apply such simple concepts as 'you are either inside
> or outside the bay'.  But reality is more complex than that.  Mapping
> them as polygons would be nothing but cargo cult towards this aim.
>
> A node tagged natural=bay means: the water around here, up to the coast
> around and out to open water for a similar distance, maybe somewhat
> further, is a bay and is named ...
>
> This is a much more accurate description of reality than a polygon.

How can a description that is definitely-inaccurate (nodes) fit
reallity better than a description that is probably inaccurate ? If
your aim is to make it clear that the map is as inaccurate as
reallity, ok. But :
* even if osm data is inaccurate, it's better for all data consumers
to interpret that data in the same way, and make the same mistakes.
Mapping bays as nodes add implementation-uncertainty on top of
data-uncertainty.
* there are surely cases where the accuracy is very good. But I still
wouldn't trust an implementation to guess the area from a node. As a
mapper I can control the osm data, not the heuristics that consumers
implement.
* even though nothing is standardized, there are ways to tag that a
geometry is fuzzy/inaccurate.

Nobody is forcing you to switch to polygons today. Go ahead and keep
using nodes if you feel it's enough; it actually is for many usecases.
But don't think that nodes describe reallity better. And let people
upgrade nodes to areas if they're willing to do the work.