[mkgmap-dev] Explanation for the mkgmap optimization options

Sat Feb 25 10:04:17 GMT 2012

Hi all,

I'm at the point where it seems that my map overcharges the GPSr (probably
too much details).
mkgmap offers some optimization options:

--reduce-point-density=NUM
Simplifies the ways with the Douglas Peucker algorithm.
NUM is the maximal allowed error distance, by which the resulting
way may differ from the original one.
This distance gets shifted with lower zoom levels.
Recommended setting is 4, this should lead to only small differences
(Default is 2.6, which should lead to invisible changes)

--reduce-point-density-polygon=NUM
Allows to set the maximal allowed error distance for the DP algorythm
to be applied against polygons. Recommended setting is 8.

--merge-lines
Try to merge lines. This helps the simplify filter to straighten out
longer chunks at lower zoom levels. Decreases file size more.
Increases paint speed at low zoom levels.
At the moment this option causes routing errors. Use only if routing
is not needed in your map.

--min-size-polygon=NUM
Removes all polygons smaller than NUM from the map.
This reduces map size and speeds up redrawing of maps.
Recommended value is 8 to 15, default is 8.

Questions:
- Could someone explain the options more detailed ?
- What are the pros and cons of the different options ?
- What is your own experience with optimization ?
- Is the routing affected by the options ?

Thanks - Klaus

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