[HOT] Use of Intermittent and Seasonal tags to Describe waterways

[Pierre Béland]

Hi Will,

I agree with your definition but looking at statistics for Mali, I would say that people do not apply systematically. It should be clear that intermittent is not for seasonal floodings.

Mali is a good place to look at, since we have mapped a lot of waterways this year for the activation. In the semi-desertic areas, north of Gao there are years without precipitations. And as expected, we  see that the tag intermittent=yes is systematically applied. In the Niger delta, south of Tombuctu and west of Gao, there are 
seasonal floodings. We would expect to only see seasonal=yes tags. But we see that both tags are used for the delta.

The following Overpass requests show how the tags are used and how we were not systematic enough for tagging in the delta.

Seasonal : 685 ways located in the Niger Delta
[timeout:180];(way["seasonal"](15.273587102218679,-3.9440917968749996,19.041348796589013,2.230224609375);>;);out meta; Intermittent : 546 ways. We see a lot of these ways located in the Niger delta. Only to ways have both intermittent and seasonal tags.
[timeout:180];(way["intermittent"](15.273587102218679,-3.9440917968749996,19.041348796589013,2.230224609375);>;);out meta;  

 
Pierre 



________________________________
 De : Will Skora <skorasaurus at gmail.com>
À : hot at openstreetmap.org 
Envoyé le : Mercredi 28 août 2013 14h36
Objet : [HOT] Use of Intermittent and Seasonal tags to Describe waterways
 


Hi Hotties, 

I'm writing about a couple tags: seasonal=* and intermittent  and would like to hear how you've used them in the field, mapping remotely, or any other HOT projects.
As I understand, intermittent is used to describe waterways and bodies of water that contain water after some storms or precipitation, otherwise it is mostly dry.
Seasonal is used to describe waterways that contain water and are flowing for a continual part of the year (like the season opposite the Harmattan and the dry season in Senegal). 
In terms of usage: intermittent is used ~688,000 times ; seasonal > 6,000 times in the planet. Admittedly, A
 quick look at the taginfo combinations show that 655,000 of the 
intermittent=yes tags were from a GNIS/NHD import (a federal govt US 
dataset). 


At the moment, as I understand the tags, here's what I currently propose for the HOT/HDM Preset 


intermittent=yes to describe that it's intermittent (intermittent=no would not used, because with OSM data, it's assumed that the mapped object is always there)


seasonal=yes (seasonal=no would not used) 


I wouldn't use both seasonal=yes and intermittent=yes for an object. If a stream or canal only has water some time of the year, intermittent=yes would suffice. 

I also propose to add these tags into the HDM tagging set - http://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Tags/HDM_preset
https://github.com/hotosm/presets/issues/12

Also, should we use these for other tags besides waterway= ? 
I'd also propose to use these 2 tags for natural=water as well.


Feedback and critiques are welcome here or on the github issue. 

Lastly, if someone could translate this for other local communities where english isn't widely spoken (Indonesia, Haiti, and many more), to hear their opinions and existing practices, I'd greatly appreciate it. 

Regards, 

will

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