[Tagging] Fuzzy areas again: should we have them or not?

[Anders Torger]

When I made the starting post I didn't have a better name than "fuzzy 
areas", and I don't really have it still, but what I meant to address 
were those areas that are coined as "non-verifiable geometry" in 
relation to the verifiability principle.

Glaciers are really hard to make an accurate outline of. I've done a few 
of those and the problem I have here in Sweden is that you need late 
summer photos to actually see where the ice is under the snow, and you 
don't get that in the free photo layers, and you also need very accurate 
topology correction of the photos, which indeed has become much better 
in recent years but still leaves more to be desired.

However, regardless of that they are generally verifiable geometry in 
the verifiability principle context. The challenge with glaciers is that 
of accuracy not of verifiability.

Bays with wide openings to the sea on the other hand, where does it end? 
That border is undefined and thus non-verifiable, and according to a 
strict interpretation of the verifiability principle, which I see 
leading OSM community members honor, those should then not be mapped as 
a polygon, but should be mapped as a point placed somewhere clearly 
inside (verifiably inside) the bay.

But let's talk about glaciers again, and other features whose challenge 
is accuracy not verifiability. These features can lead to "edit wars" if 
you have two mappers that use different sources and each of them believe 
theirs is more accurate. Why do I bring that up? Because the risk of 
"edit wars" due to conflict of how the geometry should be drawn seems to 
be the primary argument against allowing drawing of non-verifiable 
geometry. The argument goes that there would be lots of edit war so we 
would need a policing entity and by that we would through the whole 
egalitarian cooperation principle out the window.

However my answer to that is that the danger is exaggerated and we 
already have plenty of non-verifiable geometry all over the map, without 
any big issues of edit wars. They are not really much more danger than 
those features that are hard to draw accurately. And we can not just 
leave everything that out. Oh well, we can if we police it, but we're 
not really that active in that (vandalism is more important to stifle) 
and we can clearly see that mappers want to map these things, so I don't 
think we should outlaw it, but instead drop the passive resistance and 
let it evolve.

It does add value to the data. With an approximate geometry available a 
renderer can make proper decisions of how big to make a text label, and 
it's also free to move it around a bit to avoid collisions and improve 
readability. Geometry also makes queries better, if you ask the map to 
show a named bay or a plateau or forest or whatever, it can zoom to that 
place and show the proper area of the map where it is rather than 
zooming in max on a point. It shouldn't draw the outline though, as it's 
defined as "fuzzy". Queries like asking if feature X borders to feature 
Y also requires that geometry is available. Sure there can be 
inaccuracies if you ask things like "is feature X within fuzzy feature 
Y". Looking through the history there are suggestions of advanced 
features where you can define how wide the fuzzy border is so the map 
could answer "unclear" on such a question in addition to true/false, but 
I think that is overkill. I would say that inaccurate answer on border 
queries is a cheap price to pay.

It's more about if we *want* these geometries to exist or not. If we 
want them, we can have them and their issues can be managed. If we don't 
want them we can look at their specific challenges and exaggerate and 
just say no to any proposal. But it seems like we will have some of them 
anyway (they are in), unless we start policing and removing.

The problem with status quo is that there's mixed messages to mappers, 
these geometries are in there and some are rendered, and are obviously 
useful to the alternative (mapping as a point), but they are still 
according to some against the rules, so when someone wants to develop 
this further with a new tag, say for a plateau, it is at great risk of 
getting roadblocked by the same strict interpretation of the 
verifiability principle. Status quo also means a lot of passive 
resistance towards these, for example by not rendering them, like 
peninsula and valley tags today. There's one thing not rendering 
snowmobile paths and other speciality information, another to leave out 
generic map information like name of valleys, to me as a mapper that is 
a message that we really don't care about this type of general-purpose 
information or at least not if it must be made with a "non-verifiable 
geometry".

That lead me to write the somewhat confrontational heading "should we 
have them or not?" because I as a mapper is really tired of these mixed 
messages, and in my personal mapping I already use these geometries a 
lot and I am in need of more tags (plateau etc) and like others to be 
rendered (valley, peninsula...). If powerful community members intends 
to backtrack and move back to point mapping or even just continue the 
passive resistance it means that a major motivational factor to map is 
swept away for me, that of being able to properly name nature. So it 
would be nice to know where OSM is heading...

A sidetrack of this discussion is if this should be in a different 
database or not. It seems like GIS experts think it should be separate, 
but OSM is not a traditional GIS system. I'm for any solution that works 
though, but it must work seamlessly with OSM editors though as these 
geometries are plentiful and needs crowd sourcing by the mappers just as 
all other geometries.

On 2020-12-23 23:41, Graeme Fitzpatrick wrote:

> On Thu, 24 Dec 2020 at 03:27, Martin Søndergaard 
> <sondergaard246 at gmail.com> wrote:
> 
>> most interesting discussion I have seen on this list yet. And I want 
>> to give a few of my thoughts as well.
> 
> Thank you, Martin!
> 
> Excellent post & I agree entirely with what you say.
> 
> As I mentioned a while back (may have been in another of Ander's 
> threads?) - we draw an area & say that this is a town / village, but 
> what about that house 300m down the road, & the one 500m beyond that? 
> Do those people think they live in this town?
> 
> My own city is a major built-up area, but as you go out into the 
> surrounding country, you come to suburbs with acre / <hectare house 
> blocks, then a bit further there are multi acre / hectare blocks, but 
> where does the "city" end?
> 
> On Thu, 24 Dec 2020 at 03:58, Joseph Eisenberg 
> <joseph.eisenberg at gmail.com> wrote:
> 
>> * natural=glacier with ~56,000 entries
>> * place=archipelago with ~1,300 entries
>> 
>> These three are not at all fuzzy, in the mathematical sense.
> 
> I'd question a couple of those thanks, Joseph.
> 
> Glaciers are constantly moving, so how can they not be fuzzy, 
> especially now with climate change apparently melting Arctic glaciers 
> at an ever increasing rate, so their boundaries must be constantly 
> changing?
> 
> & with archipelagos, & bigger island nations, whose boundaries are 
> drawn across the open ocean - how can we be precise about that line?
> 
> Thanks
> 
> Graeme
> 
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