Arne: I will put all this in order and make the changes to the wikis,
and then come here for final tweaks.
Not only the first, but subsequent projects will be open to
enhancements, as it has happened with most of crowdsourced imports
before. I am sure we will find issues and things to improve here and there.
You are right, we can leave fixme tags. Better note than annotation. But
what Pierre was suggesting wasn't a new tag, but rather using the
intermittent tag to give more info. But it will be complicated anyway to
know that info, as it is impossible to know the smoothness tag value for
a highway unless we have on the ground info.
Cheers, and we wait for you to come back,
Rafael.
O 09/04/20 ás 19:56, Arne Kimmig via Imports escribiu:
Hi Christoph and Rafael,
I agree with Christoph that only somehow active rivers should be
mapped as waterways.
I mapped a few (not all) rivers in the import area only where I saw
some erosion banks or gullies.
See https://www.openstreetmap.org/#map=13/2.7975/41.1247 for some
examples and compare them with the rivers to be imported.
At a first glance it seems to me that mapping only rivers with
erosions features leads to a much less connected river system than the
one represented by the import data. Which one represents reality better?
For practicability and to come to action I would think that we did
discuss all important aspects of this river import and I would propose
that we should start with the first subproject as a kind of prototype
when the workflow is ready. Performing the import and correcting the
data we could discuss further and gather new experiences to improve
the workflow and the mapping quality for the subsequent parts.
Just one more remark concerning tags: I’m not a friend of inventing
new tags like intermittent=decade or so. For questionable rivers I
would instead use an [annotation="maybe old riverbed"] or a
[fixme="confirm active river?"] or similar to show that local know how
is needed.
For the next about 2 weeks I will be off somehow for this project but
afterwards I’ll come back.
See you and regards
Arne
Am 09.04.2020 um 18:33 schrieb Christoph Hormann <[email protected]
<mailto:[email protected]>>:
On Thursday 09 April 2020, Rafael Avila Coya wrote:
If a river gets dry for any reason (let say for some decades ) but u
could still see the river course (which is only possible in very rare
occasions) u could still call it a river just to maintain the
landmark notation and geography."
I have not made a statement on what can be called a river and what not.
That is a speciality problem of English language semantics. What i
said is that a feature that shows no verifiable water flow in present
times is not to be tagged as waterway=*.
I am not an expert, and I would do what Arne suggest if I was mapping
without discussing this with anybody, but still, like Arne, I see the
lack of a tag for these kind of rivers.
Feel free to introduce a new tag for something verifiable for which no
tagging exists yet. But you should keep in mind that there are already
a lot of tagging ideas in that wider domain that have either failed or
are used without a well defined meaning:
https://wiki.openstreetmap.org/wiki/Tag%3Awaterway%3Dwadi
https://wiki.openstreetmap.org/wiki/Tag:waterway%3Ddrystream
https://wiki.openstreetmap.org/wiki/Tag:natural%3Dvalley
As for the Lagh Dara, this colleague has sent me two images of the
rivers passing by Afmadow town.
One shows the river as we can see it normally:
https://flic.kr/p/2iNyA5a
But the second shows how it was during the 2018 devastating
floodings: https://flic.kr/p/2iNyA7z
He has been on UN missions in Somalia many times, so he has too on
the ground knowledge.
By the way: the Lagh Dera river geometry is right now of very poor
geometry in OSM, while the UNSOS one is very good in comparison:
https://flic.kr/p/2iNyQ6G
Please keep in mind that anecdotal examples are not representative for
the whole. I could easily provide a dozen examples for the existing
mapping being fairly accurate and the import data being off by at least
50-100m.
Flooding is a completely different subject. We do not map 2/3 of
Bangladesh as water just because it becomes flooded on a regular basis.
waterway=river/stream is for mapping localized, verifiable surface
water flow, it might be seasonal, it might be ephemeral - but it needs
to be there. What your example image shows is specifically the lack of
water flow over longer distances. Water from heavy local rain does not
drain on the surface along the supposed river but accumulates in local
depressions as temporary lakes.
Overall i think we are departing from the matter of import review here.
--
Christoph Hormann
http://www.imagico.de/
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