[Tagging] How to tag small canals?
61sundowner at gmail.com
Sat Aug 18 23:29:21 UTC 2018
On 19/08/18 04:01, Martin Koppenhoefer wrote:
> sent from a phone
>> On 17. Aug 2018, at 13:43, Christoph Hormann <osm at imagico.de> wrote:
>> If you want to map the river width tag width=*, if you don't want to map
>> the width then don't create classes based on width thresholds.
> river size is not about width alone, the most generic approach to measure size is looking at the quantity of water per time. It accounts for width, depth, flow speed in one parameter. For the significance, length is probably also interesting.
> The width alone depends on factors like the terrain and its geology.
> These numbers are most useful in relation to other waterways nearby. The context matters, the same amount of water in one area might be a stream and in another a river.
> Usually at the confluence the name of the waterway with the most water is the one whose name prevails, but sometimes there are exceptions, e.g. for historic reasons (e.g. they didn’t know exactly which river brought more water, or considered one more important for other reasons)
> For navigation it is interesting to know if you can cross the waterway without bridge, tunnel or ford by jumping over it (width) or by walking through it (depth).
Of course there are exceptions.
The Todd River in Alice Spring Australia has had 0 width and 0 flow every time I have been there.
And you can walk across it, camp in it .. play games in it. Most of the time.
Yet it is a river as can be seen by the width of the sandy river bed and the length of the bridges crossing it.
And when water does flow in it you don't want to be in it .. even in a boat.
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