[mkgmap-dev] Explanation for the mkgmap optimization options

Sat Feb 25 15:51:43 GMT 2012

I use normally --reduce-point-density=1 --reduce-point-density-polygon=1 
--merge-lines. I have no problems with routing. (I also use 
--remove-short-arcs=3)

Basically --reduce-point* -options simplify the shape by removing some 
of the points if it does not affect the shape too much. I have no 
problems with drawing speed but I keep the very low optimization on to 
take care of any exessive details. (Consider for example a road that has 
points every 2m and the poor GPS trying to draw that on a moving map)

Pro of optimization is faster map drawing and smaller map files. The con 
is reduced details and perhaps a bit coarser map (depending on how much 
you reduce point density).

A test with my personal style file and different options (using same 
data for Finland and the latest mkgmap):
-options at 1m: size is 110 MB
-options at 4m: size is 107 MB (a bit too coarse map for my taste)
-no optimization: size is 109 MB

You may benifit more or less on your region. In my region I consider the 
result that the size is not really affected but it simplifies anything 
overly complicated.

I have no idea why the map size is increased (by a tiny bit) with my 
options at 1m compared to no optimization.
--
Harri