On 04/28/2012 09:23 PM, Paul Norman wrote:
From: Nathan Edgars II [mailto:[email protected]]
Sent: Saturday, April 28, 2012 2:24 AM
To: Tag discussion, strategy and related tools; OpenStreetMap talk-us
list
Subject: [Talk-us] Waterway directionality in drainage canals
It's the standard to draw a waterway in the direction of flow. I've
questioned this several times, but it's an ingrained default.
My question is more specific: what happens to a drainage canal that
reverses direction? I offer the Everglades and surrounding agricultural
land as an example. There are huge "water conservation areas" that store
water. When it rains, gates are closed and opened to direct water into
these. During a drought, gates send water back out into the canals for
local use. When there's a big storm, water will instead go directly out
to sea.
So there are a lot of major canals that have no fixed direction. How
should these be mapped? Is there any existing scheme that can show how
water flows under different conditions?
The same issue came up with minor drainage ditches and cranberry fields
here. They're used to drain sometimes and sometimes to flood the field for
harvest.
I came up with the proposal
http://wiki.openstreetmap.org/wiki/Proposed_features/directional for
directional=* but it's abandoned.
One weakness with the proposal is that unknown values are a special case of
directional=no, not directional=yes
How about the oneway property? That is already often used on rivers (not
so often on streams), but an explicit "oneway=no" would specify that
water may flow in both directions... Just an idea.
--
Cheers,
Alex
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