[OSM-talk] Mapping rivers that flow into/through lakes?

Matej Lieskovský lieskovsky.matej at gmail.com
Fri Feb 23 08:01:21 UTC 2018

```Greetings!

I saw a nice argument somewhere about the lines for larger rivers that
might be applicable here:
Imagine if the water level dropped significantly - the areas would be off
(but should be kept at their normal level unless the change is likely to be
reasonably permanent) but the lines should stay reasonably accurate,
mapping the main channel where the water will keep flowing. Of course,
unless the water drops it might not be possible to find out where such a
channel is exactly, so the map usually contains our best guesses.

Happy mapping!

On 23 February 2018 at 06:53, Maarten Deen <mdeen at xs4all.nl> wrote:

> On 2018-02-22 22:59, Rory McCann wrote:
>
>> Hi mappers,
>>
>> What's the best way to map rivers that flow into lakes, especially when
>> another river flows through it? Should they be connected?
>>
>> When a river flows through a lake, you can map a waterway=river way
>> through it, to be "topoligcally complete". Or would it be better to add
>> ways (w/o waterway tag) to the river relation?
>>
>> When a tributary river joins another, join the central waterway=river
>> ways together. But what if a river drains into a lake with a  "central
>> river" through it? Should you connect that river to the central river?
>> It makes topological sense.
>>
>> If you asked someone "Where does this river end?" they'd probably point
>> to where it joins the lake. Connecting the river to the "central river"
>> breaks this. And it can result in odd long ways. I might have gone a
>> little OTT here (
>> http://tools.geofabrik.de/osmi/?view=water&lon=27.98062&lat=
>> -16.95179&zoom=11
>> ) or here (
>> http://tools.geofabrik.de/osmi/?view=water&lon=-8.26705&lat=
>> 52.99047&zoom=11
>> ).
>>
>
> I see nothing wrong with those examples, I would do it the same,
> especially if the rivers can be sailed on by boat. Then you absolutely need
> the rivers to be connected to a central river (or fairway) in the lake.
>
> Maarten
>
>
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