[mkgmap-dev] splitter maximum tile size

Mon Dec 3 21:24:02 GMT 2012

>
> I think my testcase is not ideal. I have used a polygon that covered the
> whole tile. But this causes large (too large) img sizes because the
> polygon has to be split into many subpolygons when mkgmap splits into
> subdivisions.
> I think instead it is better to use one POI node in each corner of the
> bbox. I will try again and report about my findings.
>

I've played around a bit more.

mkgmap is able to compile a single tile that covers the whole planet 
wihtout any error messages or exception. But that works only if 
--transparent is used. If --transparent is not set mkgmap creates the 
background polygon that must be splitted in so many smaller parts so 
that the maximum tile size is exceeded.

But such large tiles are not displayed by Mapsource and Basecamp. They 
display mkgmap generated tiles only if the longitude and latitude tile 
size is below 179.9x°. I didn't measured the exact x (179.9° works, 
179.99° does not work).

So a tile with the bounds
<bounds minlat="-89.0" minlon="-10.0" maxlat="90.0" maxlon="169.9"/>
can be compiled and displayed with MapSource and Basecamp.

A tile with the bounds
<bounds minlat="-89.0" minlon="-10.0" maxlat="90.0" maxlon="170.0"/>
can be compiled with mkgmap but no data is displayed in MapSource and 
Basecamp.

So splitter could use a max limit of 179° for lat and lon but I don't 
know if that makes sense at all.

WanMil