If you create a separate map for buildings or contourlines only - usually there is no need for an overview map - or better no need for any content in the overview map - or am I missing something?

Because those maps sometimes may have very large tiles, but very few levels (maybe only 24) - mkgmap creates an overview map at the next resolution - and will then often throw warnings such as:

SEVERE (OverviewBuilder): Tile selection (0x4a) polygon for tile 84900000 cannot be written in level 0 resolution 21, using 20 instead

There is still a need for an empty overview map - as without it you cannot show the map in Basecamp/Mapsource - or transfer it with MapInstall.

I know the overview map is only empty 0x4a polygons - just wondered if there is a better solution...

--overview-levels=

is not given.

Felix Hartman - Openmtbmap.org & VeloMap.org