[mkgmap-dev] Analysis of finnland mp seabounds processing

Sat Jan 30 21:45:26 GMT 2010

Hi WanMil,

> The generation of the sea polygons with  
> --generate-sea=multipolygon,no-sea-sectors sometimes still produce  
> flooded areas.

What are the sea sectors good for, and why are you disabling them?

> 1. Some of the inner polygons generated for the seabounds mulitpolygon  
> sometimes are inverted. Usually the inner polygons should denote all  
> natural=land but some point out the sea are. This causes the flooding.

Am I right assuming that mkgmap is generating multipolygons for sea regions?
I downloaded some of the map area covered by your GPX file, and not all
coastlines of islands were part of a multipolygon relation.

> 2. Some islands seem to be tagged with natural=land. They are not  
> considered in creating the sea multipolgyon.
> Example: http://www.openstreetmap.org/browse/way/48666101

Could mkgmap ignore the natural=land when generating the multipolygon?

> Hope these two things help to reduce the flooding.

How should we proceed?  I can devote some time to fixing broken multipolygons
if mkgmap gives me good diagnostic messages.  I have already fixed all the
roundabouts and turn restrictions that mkgmap complained about in Finland,
over the course of some weeks.

	Marko