Thanks Steve, So, as I understand it, I need to change the default relation style file in order to convert those multipolygons into lines?
When I look at other osm maps from the same area (openmtbmap, radfahrers map, computerteddy) I dont see those connecting lines between the borderlines. Looking at their style files I don't see a difference in how they handle the borders compared to the default style. So... how do they do this, if they use exactly the same osm data?
If anybody who want to test it out, I put the osm data here: http://moh.freehostia.com/osm/nassau.osm (200kb, I only downloaded the border polygons of the municipality of Baarle-Nassau). Or an even more simple example can be found at http://moh.freehostia.com/osm/simple.osm (3kb) The last one is not real osm data, but a simplification of the situation.
Minko, the connecting lines are generated by the multipolygon code of mkgmap. It must divide each outer polygon into two halfs to cut out an inner polygon because we don't know a multipolygon type which is supported by the Garmins. We only know garmins single polygon type. So what you see are the cutting lines created by the mkgmap multipolygon code. WanMil