[Tagging] Way inside riverbank

fly lowflight66 at googlemail.com
Tue Apr 14 11:09:28 UTC 2015

Am 14.04.2015 um 12:52 schrieb Christoph Hormann:
> On Monday 13 April 2015, Torstein Ingebrigtsen Bø wrote:
>> Hi,
>> I'm currently importing topological data of Norway to OSM. From the
>> data set we have riverbanks; however, we do not have the deepest
>> middle way as required by the wiki [1]. This middle line is therefore
>> drawn manually. This is a time consuming (and dull) job. For one
>> municipal it takes around 5-10 hours to draw all these lines, in
>> Norway we have 428 municipals. Drawing all these middle lines will
>> slow down the time to import everything dramatical. I am therefore
>> curious of what is the benefits of this line. Is it really necessary
>> or is it a "nice to have"?
> It is the other way round - the riverbank polygon is optional and 'nice 
> to have'.  The waterway line is what actually defines a river in OSM, 
> it also gets the name tag and other attributes.  The primary reason for 
> this is to map the water flow structure.  Also it is much easier to 
> verify and fix structural errors in waterway line mapping than for 
> water polygons.
> Generating a waterway line when you only have polygons is fairly simple 
> via straight skeletons (http://en.wikipedia.org/wiki/Straight_skeleton)  
> If the source data set does not contain continuous line features for 
> rivers generating those should be part of import preparation.  And i 
> disagree with Janko here - if the source data does not contain certain 
> information that is required according to OSM mapping conventions you 
> should not import the data unless you produce the information in some 
> way (either through manual mapping, computing the missing data or 
> getting it from other sources).  Otherwise the data becomes dead mass 
> in the OSM database.


Thanks for the wording.

Cheers fly

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