[OSM-talk] Slippy map - Mapnik layer UK coastlines

Mike Collinson mike at ayeltd.biz
Sat Mar 24 04:03:47 GMT 2007


At 09:48 PM 23/03/2007, Artem Pavlenko wrote:
>Hi David,
>
>On 23 Mar 2007, at 11:48, David Groom wrote:
>
>>It seems that the UK coastline is beginning to render better in the Mapnik 
>>layer of the slippy map (it's a solid blue fill, rather than the odd shaped 
>>grey polygons).
>>
>>However it does appear that the source for the coastline might be a rather 
>>out of date planet file.
>>
>>In some places, eg 
>><http://www.openstreetmap.org/index.html?lat=50.85383936185782&lon=-1.315713476905844&zoom=15>http://www.openstreetmap.org/index.html?lat=50.85383936185782&lon=-1.315713476905844&zoom=15 
>>,there is an exact correlation between coastline which is shown in the 
>>Mapnik and Osmarender layers.
>>
>>In other places eg , 
>><http://www.openstreetmap.org/index.html?lat=50.81094579389664&lon=-0.09869895092239864&zoom=15>http://www.openstreetmap.org/index.html?lat=50.81094579389664&lon=-0.09869895092239864&zoom=15 
>>,the coastline outline in the Osmarender layer seems to be much more recent 
>>than the Mapnik layer.
>
>For most of the world I was using original shoreline data, hence it's not as smooth as it should. Polygons are only available for England and Wales, the rest gets blue shoreline lines.  To have proper polygons for the whole planet :
>
>1. We need to agree that storing countries boundaries as polygons is way forward.
>
>2. We have to decide if storing these polygons in main OSM database is a good idea or not. I personally think it'll be better to store them separately. 
>
>3. Start creating polygons. I have all the tools and I'm happy to help anyone, but it is a big task which requires community participation.
> On the other hand, If one person capable of fixing most of the UK coastline it should be peanuts for OSM as a whole. If you want to see nice blue sea and land just do it, don't wait!

[Sorry, David, I am responding to Artem's comments, not your original issue!]

 From the perspective of a contributor and editor of OSM data rather than technical,  I'd certainly endorse storing coastline data separately.  Currently, it takes forever to get the data uploaded in the first place, greatly slows down downloads of an editing area of interest when I have no interest in editting the coastline, and when I am editting it is extremely fiddly and user-error causing when it crosses other data.

I'd see the advantages as:

        - Gives ability to store more than one coastline set

        - To be able to retrieve it as a separate layer would make coastline maintenance much easier.

        - Makes general editting easier

        - Protects it from mistakes when doing general editting, which will become important if we encourage "drive by" editing of our data by the general public.

        - A good test bed for determining whether general separation is a good thing (political boundaries, bus routes, specialist POI sets, ...) and for enhancing edit and rendering tools to cope.


Mike



         
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