[mkgmap-dev] Request - set --reduce-point-density= for each resolution

Wed Apr 28 04:03:38 BST 2021

As I'm not sure everyone is following the other topic, I would like to ask
to introduce the possibility to set different values for the DP filter
based on resolution.

Why is this important?

a) maps which are produced with resolution 23 as highest resolution need to
have a much lower level than subsequent resolutions.
b) For resolution 23 and 22 a lower level makes sense - it is not needed as
much here to speed up the gps device map drawing speed, while for lower
resolutions like 18-21 a high level is really needed else map panning
becomes painfully slow (usually basemap kicks in at 17).

If I'm correct right now 2.6 at resolution 23 would be 5.4 at resolution
22, 10.8 at resolution 21 and so on. It's okay to keep that behaviour - but
the value doubled just needs to be possible to be set for each resolution.
It doesn't matter to me if we keep it like that or if we change the numbers
than ourselves by resolution. Important thing is that it's possible to be
set for each resolution

c) maybe also introduce the possibility to set DP for resolution 24. I
think a value of 0.3-0.6 could be worth it. I'm not sure if there were some
problems preventing DP to be used at 24. However as by now I think mkgmap
is able to produce routable maps starting at 23 instead of 24, those
problems should be fixed...
In general I think a map made for automotive use (car, motorcycle) would be
fine using resolution 23 as a start instead of 24. Like Garmin City
Navigator maps do. But then yes it's really important to not have a high DP
value on resolution 23. Same as contourlines only maps which make sense at
resolution 23 instead of 24.

-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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