[mkgmap-dev] Sea generation

Fri Nov 5 21:28:05 GMT 2010

OSM version of Mapnik's high-resolution coastline shapefile is here:

http://planetosm.oxilion.nl/~lambertus/coastline.osm.gz (584 MB)

Op 05-11-10 18:14, WanMil schreef:
> Thanks for all feedback! That's great!
>
> Looking at the discussion I think the idea of an extra coastline file
> has the highest priority.
> I think the implementation will mostly follow the suggestions of
> Apollinaris Schoell:
> - coastline input file(s) will have OSM format
> - natural=coastline tag will be removed from all other tile data
> - the coastline data is processed by the current sea generation
> algorithms using the multipolygon algorithm
> - for each tile the resulting big multipolygon is clipped to the tile
> borders and added to the tile data
>
> Using this algorithm it should be possible to have multiple coastline
> input files (e.g. one for the Mediterranean Sea, one for Atlantic Ocean
> etc.) The only condition is that the coastline files define complete
> polygons. So the Mediterranean Sea file would have to add a coastline
> tag crossing the Strait of Gibraltar. The polygons itself might consist
> of multiple ways as it is used in the original OSM data. The sea
> generation algorithm connects them to polygons.
>
> Some add ons maybe implemented later:
> - shp support for input (is that needed? better preprocessing?)
> - mp algorithm with land polygon
> - comparation between the coastline input files and the OSM tiles with
> automatic adaption of changes that doesn't flood the tile
>
> Please let me know if you have some additional ideas for this and the
> sea generation in general.
>
> Have fun!
> WanMil
>
>
>> Hi all,
>>
>> I have started to rework the sea generation code. There have been
>> several reports of problems with flooded tiles in the last weeks so I
>> think it is neccessary to improve some parts of it.
>>
>> The first thing I've started is to implement a flooded tile blocker. The
>> algorithm has been discussed a while ago on this list. It uses a
>> quadtree implementation which is able to return all points contained by
>> a polygon. The quadtree is filled with all highway points. If a sea
>> polygon contains too many points that belong to highways something is
>> wrong and the sea polygon is discarded.
>>
>> That's the idea... Let's see how it works.
>> The quadtree might also be used to correct wrong sea polygons. But
>> that's one of the further steps.
>>
>> Do you have any other ideas how to improve the sea generation and how to
>> make it more failsafe? Then please let me know.
>>
>> Have fun!
>> WanMil
>>
>> _______________________________________________
>> mkgmap-dev mailing list
>> mkgmap-dev at lists.mkgmap.org.uk
>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>>
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev