[OSM-talk] mkgmap confusion: zoom, resolution and levels.

[simon at mungewell.org]

I'm hoping someone can clarify this for me....

So my device (Etrex Vista mono) has buttons on the side which zoom the map
in and out. Reading the mkgmap page these are described as resolution
states, values between 1 and 24 with 24 being the most detailed
resolution.

The map-features file contains a value for the minimum resolution value at
which a feature is present.

However there is also the levels concept; which is what I'm having trouble
getting my head around. Where the downloadable map contains different
levels, which are rendered according to 'zoom' state (or something like
that - what do I know... I'm confussed).

Does this mean that the steps (zoom state where things become visible) are
limited to the number of levels, or are the minimal resolutions respected
despite the number of levels.

If the later, what is the point of having the levels concept?

Example:
If I have feature1 at 18m, feature2 at 20 and levels set to
0=24,1=22,2=16,3=14. Will feature1 and feature2 first appear at the same
zoom state or at different zoom states?


Lastly (on the assumption that it saves space or speeds up rendering) is
there a way to reduce the complexity of a feature for lower resolutions?

I am thinking that my major contour lines could be significantly smoothed
at lower resolutions, whilst maintaining their full resolution at high
resolution.

Cheers,
Mungewell.