[Tagging] Waterway length

[marc marc]

Le 16.02.19 à 22:32, Sergio Manzi a écrit :
> A static value for a river length in OSM, without any information about 
> its source

every tag you add into osm have a changeset with a source tag, isn't it?
so adding the lenght should/must also have a source (extrapolation (sum 
of all way of a relation) of osm data is a source)

a few month ago, I have checked the length of Rhône [1]
the french wikipedia list 2 sources for the lenght... both are very fair 
away of the lenght found after some work on osm data.
which one to choose? osm without hesitation. maybe it is not fair but at 
least it is verifiable (everyone can load the relationship, see the 
result and correct errors if necessary) while the other 2 sources 
(including the official French source) are totally unverifiable.

unfortunately I did not send in osm the result of the cleaning because 
it concerned partly errors in osm (mainly roles in the relationship)
but I started by purging everything that didn't interest me in the 
relationship before fixing. it will have to be done again

[1] https://en.wikipedia.org/wiki/Rh%C3%B4ne