[Tagging] Rio de la Plata edit war

David Groom reviews at pacific-rim.net
Fri Aug 7 00:52:40 UTC 2020

I've so far stayed out of this discussion because my final thoughts on 
the matter will I am sure be contentious.

In no order of importance my thoughts are:

1) the idea of basing a the limit on coastline on levels of salinity or 
average water flows makes as little sense as trying to specify that the 
"landuse = forest" tag can only be used when there are a specific number 
of trees growing in a particular area.

2)  yes the wiki says coastline should be based on the Mean High Water 
Spring, but I've long argued that for instance no one in London would 
say they lived on the coast even though the River Thames is tidal 
upstream of the city.  Hence the border between coastline and water body 
should be downstream of the tidal influence and is based on "a 
reasonable estimation of where an observer might suggest the river ends, 
and the sea begins".  Such an estimation is imprecise, not subject to 
verification, and different observers will have different opinions - get 
over it.  As in point (1)  different observers will have different 
opinions on where a "forest" ends and "scrubland" starts.

3) Due to the needs of the rendering process we have long established 
that ways tagged "natural = coastline"  are a special case.

4) We have existing tags for "tidal = yes" and "estuary=yes", 
"admin_level = ?" which means it is unnecessary for the coastline tag to 
be used as a proxy for these.

5)  The discussion on what the tag "natural = coastline" actually means 
has been discussed for so long that it appears almost insolvable.

Given the above.

A) In view of all the points above it is not possible to write a concise 
definition of what the tag natural = coastline" represents.

B) Until January 2020 we had a reasonably broad agreement on where the 
coastline should be.  Though I recognise, perhaps more than most who 
have contributed to this thread, that there are still are large number 
of ways ( particularly in the more sparsely populated areas of the 
world, or where the OSM community is not large)  that are unchanged from 
the position they were placed in by the PGS imports in 2006.

After much thought my, probably contentious, view  is:

1) We should establish an agreed "OSM Coastline position", which I 
suggest would approximate to the position of the coastline on 1 January 

2) Any edit which moved the position of the coastline by more than 20Km 
from the established position should be classed as vandalism, unless 
such movement had previously been agreed by the community.

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