[mkgmap-dev] The 0x4b background polygon in the overview map

Fri Jan 12 12:44:11 GMT 2018

Hi Gerd,

using poly to clip background could be a way to create irregular maps. 
There are some caveats.

Background doesn't clip map data, they will be still visible. The proper 
way would be to clip data too.

Detailed tiles and overview map have different resolution and usually 
their edges don't match. It is visible in BaseCamp and Mapsource.

Mapsource (maybe BaseCamp to) calculate routes only inside background 
area. I think overview background is used for estimating this area at 
some zooms. If overview doesn't cover full map or there are holes, then 
some area can be excluded as destination of calculated route, program 
will use direct routes instead.

All this said, I like clipping DEM in overview map, but I don't think 
that clipping background will improve maps unless you clip data in 
detailed tiles.

-- 
Best regards,
Andrzej