[mkgmap-dev] Options

Mon Dec 10 13:29:05 GMT 2012

> What sub-options to generate-sea does everyone use? Are the defaults
> most likely to result in an un-flooded map or does it depend too much
> on which part of the world you are creating a map for?
>
> ..Steve

Hi Steve,

I'll try to go more into detail of the suboptions:

multipolygon and polygons/no-mp are mutual exclusive.
Using multipolygon the land and sea is modelled as one big multipolygon. 
So islands are cut out from the sea and that leads to some well known 
multipolygon artefacts.
Using polygons the whole tile is covered with a sea polygon and all land 
area is added as polygons tagged with natural=land (the tag can be 
changed with the land-tag parameter). The advantage is that you don't 
have the multipolygon artefacts. Disadvantage is that sea polygon covers 
the whole tile.
no-mp is the same al polygons. I think we should remove that.

no-sea-sectors and extend-sea-sectors are required on the edges of a 
data extract, e.g. compile a map with the data of France. So you have a 
tile with coastline data of France that stops on the border of Belgium. 
So the data is incomplete and the sea-sectors algorithm tries to guess 
how the coastline is closed best. I guess the description of the 
extend-sea-sectors parameter (same as no-sea-sectors) is wrong but I 
must check that in the code.

close-gaps repairs missing coastline data.

All floodblocker options configure the floodblocker. This prevents the 
sea-generation if it detects that too many streets or other things are 
located within sea polygons. Maybe the fbdebug parameter could be 
removed and replaced by an entry in the log properties.

WanMil