[Tagging] Tagging "natural" borders

Erik G. Burrows erik at erikburrows.com
Mon Aug 23 18:48:22 BST 2010


Thanks Michael and Liz.

I've been thinking about this for a while, and putting off mapping many of
the streams/rivers in the Sierra Mountains because of this uncertainty.

It seems that there is no general consensus, so I would like to propose
what I think is the best trade-off:


I think that if we map the park/city/etc boundary as a separate way than
the river/ridge/etc, we give ourselves greater flexibility over time:

1. We don't know for certain if the boundary is defined as the
river/stream center forever, or if it was defined as the center at a
certain point in time.

2. When the city boundary changes for political reasons, or the river
changes course due to erosion, it is much easier to represent this without
having to split the natural way from the boundary polygon.

3. Most renderers draw line features on top of polygon features making the
rendering nicer looking

4. I don't think a simple mathematical offset is the best way to represent
the two ways, but rather a more natural mapping of the natural feature:
peak-to-peak or following the river, etc.

Sound reasonable?

-Erik

> I'd prefer relations.  Duplicating the line to offset is borderline
> micro-mapping; I don't think micro-mapping is practical in a lot of cases
> right now.
>
> On Tue, Aug 10, 2010 at 3:08 PM, Erik G. Burrows
> <erik at erikburrows.com>wrote:
>
>> >> I have several cases where a border polygon (national park,
>> wilderness,
>> >> etc.) is defined based on a natural feature, such as a
>> >> stream/crestline/etc.
>> >>
>> >> What is the preferred way to handle this dual-purpose way?
>> >>
>> >> Splitting the border way, creating a relation of the border pieces,
>> and
>> >> adding the natural= tag to the correct pieces seems reasonable to me,
>> >> but
>> >> I want to make sure that is correct, and will render properly.
>> >
>> > Depends how the border is defined. Is it the stream centerline? One
>> > bank? A parallel offset line on one side? (The latter is probably more
>> > applicable to canals where the property line goes beyond the water.)
>>
>> In the cases I'm dealing with now, the boundaries are on the stream,
>> which
>> is not defined anywhere as having width, just a line.
>>
>> --
>> If you are flammable and have legs, you're never blocking a fire exit.
>> -Mitch Hedberg
>>
>>
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-- 
If you are flammable and have legs, you're never blocking a fire exit.
-Mitch Hedberg




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