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

Keith Sharp kms at passback.co.uk
Fri Mar 23 18:20:00 GMT 2007


Hello,

I'm certainly interested in helping with this.  I was thinking we need
to do some work to improve coastline modelling and rendering.

I think countries as polygons is the way forward, and but I think that
it is probably best to prove this by demonstrating it works first.

How much data are we talking about, for the world, for the UK?

Now that I have my PostGIS + Mapnik stuff working I'm happy to try this
out locally and produce some images that we can use to argue the pros
and cons.

How should we proceed?

Keith.

On Fri, 2007-03-23 at 17:56 +0000, Artem Pavlenko wrote:
> 
> On 23 Mar 2007, at 17:10, David Groom wrote:
> 
> > ----- Original Message ----- 
> >         From: Artem Pavlenko 
> >         To: David Groom 
> >         Cc: talk at openstreetmap.org 
> >         Sent: Friday, March 23, 2007 1:48 PM
> >         Subject: Re: [OSM-talk] Slippy map - Mapnik layer UK
> >         coastlines
> >         
> >         
> >         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 out of date planet file.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 
> >         > ,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 
> >         > ,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!
> >         
> >         
> >          Cheers,
> >         Artem
> >         
> >         > 
> >         > David 
> >         > 
> >         > 
> >         > 
> >         > 
> >         > 
> >         > 
> >         > _______________________________________________
> >         > talk mailing list
> >         > talk at openstreetmap.org
> >         > http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
> >         > 
> >         > 
> >         
> >         Artem Pavlenko
> >         http://mapnik.org
> >         
> >         
> >         
> >         
> >  
> > 
> > 
> > My original query remains, since both areas I was referring to are
> > in the UK, about 70km away from each other.
> > 
> For Southampton area I used coast-line from OSM and Brighton uses
> original shore-line data.  Polygons are tiles by 100x100km. 
> 
> > I  can see advantages and disadvantages to storing polygons in the
> > main OSM database.  One disadvantage I guess is it will dramatically
> > increase the amount of data in the database, but I presume it would
> > have the advantage that the polygons can be edited / amended using
> > the usual OSM tools, so that alterations could be made by people
> > with local knowledge
> > 
> Agree. But if we want to edit boundaries we need to improve OSM tools
> to be able to handle geometries such as Polygons, basic topology
> checks etc.  All libraries are out there - JTS for Java and GEOS for c
> ++.  And of course data model thingy :) . There is no official way to
> store Polygons with loops (holes) with current data model AFAIK.
>  
> > Once 1) & 2) are agreed I'd be happy to assist if I can.
> > 
> Me too! 
> 
> 
> Cheers
> Artem
> 
> > David
> > 
> > _______________________________________________
> > talk mailing list
> > talk at openstreetmap.org
> > http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
> 
> Artem Pavlenko
> http://mapnik.org
> 
> 
> 
> 
> 
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk





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