[Imports] Antarctica coastline/shelf-ice import

Glen Barnes barnaclebarnes at mac.com
Fri Mar 8 22:02:00 UTC 2013


Unfortunately I sent this directly to Jochen instead of the list - Applogies for that.

On 8/03/2013, at 9:29 PM, Jochen Topf <jochen at remote.org> wrote:

> On Wed, Mar 06, 2013 at 07:15:10AM +1300, Glen Barnes wrote:
>>> One important difference from the current tagging is that we propose to tag
>>> the "calving line" instead of the "grounding line" as natural=coastline. This
>>> makes a lot of sense, because for most purposes the "water" side of the new
>>> coastline allows typical water use (such as moving about on a ship) while the
>>> "land" side of the new coastline allows typical land use (such as building
>>> a settlement). This change in tagging will affect all OSM map of Antarctica
>>> right away. After the import we have the data available to add specific
>>> rendering for shelf-ice allowing a much improved OSM map.
>> 
>> This concerns me a little bit. What happens if someone wants to create a map of the world and uses the coastline data to generate the continents? Won't Antarctica be incorrect? I'm not sure I see the point in tagging something that is not a coastline as a coastline. Why not just tag it as what it is?
> 
> There is no such thing as "the coastline". There are many "lines" that can
> be seen as coastlines. Generally in OSM the mean high water line is used.
> Our "interpretation" is actually consistent with that in a way.
> 
> Christoph and I have debated this for a long time. See the current state
> of the discussion here:
> http://wiki.openstreetmap.org/wiki/Antarctica/Tagging
> 
> If you have any arguments against this, please add them to the wiki page
> or discuss them on the Imports list.
> 
> Jochen
> -- 
> Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298

I'm trying to get a better handle on how this works in practice vs. other maps of Antarctica. If we look at a satellite view and map view from Google maps the coastline seems to be the grounding line although I may be mistaken:

https://www.evernote.com/shard/s2/sh/7b73b236-ed86-4331-8acf-7b6bb416a9a5/9e02240d36230c2de08a174c6369256d

Are you saying we make this whole 'bay' disappear by tagging the coasting line as the edge of the ice as opposed to where grounding line? I propose tagging the coastline as the grounding line and the ice shelf as an ice shelf. In that way you are describing what the real world is rather than a perceived value. The grounding line seems to me to represent high tide of the actual unfrozen water.

Glen



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