[mkgmap-dev] mkgmap-dev Digest, Vol 153, Issue 40 Resolution 23 raster problems

Wed Apr 28 13:13:20 BST 2021

Hi Felix,

your screen shots only show contour lines but the patch works on all types of lines and polygons. So, please also check the results with other maps.

Gerd

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Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Felix Hartmann <extremecarver at gmail.com>
Gesendet: Mittwoch, 28. April 2021 04:54
An: Development list for mkgmap; Andrzej Popowski
Betreff: Re: [mkgmap-dev] mkgmap-dev Digest, Vol 153, Issue 40 Resolution 23 raster problems

forgot 1.3 value - that is good enough (and this location is not the most difficult, but there are very few places that are worse. So I feel it's good enough as if it's fine here - there are very very few other places that are still problematic.

On Wed, 28 Apr 2021 at 10:50, Felix Hartmann <extremecarver at gmail.com<mailto:extremecarver at gmail.com>> wrote:
Thanks for that patch, the improvement is not as big as from the previous patch - but there is some.
I analysed it a bit more - and I think there needs to be one more change - actually in general and not only for contourlines.

We need different values for the douglas peucker algorithm depending on resolution!

Right now we can only set one value, and that is multiplied for each resolution?
Based on the current state I would like to have

resolution
24= 0.0 or maybe actually have it active at 24 as well trying a value of 0.3 or so. Where there any problems with autorouting or why is it not possible to use it at resolution 24 as well?
23=1.3
22=2.6
21=3.9
20-11=5.4

Especially if we produce a map without resolution 24, then resolution 23 needs to have much lower DP value than the subsequent resolutions. Using 1.3 for resolution 23 makes the quality IMHO good enough to be used for an contourlines only map for GPS devices and skipping resolution 24 altogether. For Desktop use resolution 24 may still make sense for contourlines - but even then the difference is only in very steep areas.

Attached some screenshots at resolution 24, and at 23 with different DP values and one of patch2.

On Tue, 27 Apr 2021 at 23:16, Andrzej Popowski <popej at poczta.onet.pl<mailto:popej at poczta.onet.pl>> wrote:
Hi,

some more experiments, see attached patch. I have tried to optimize
rounding of coordinates for lowest distance to line. This is not good
for polygons, because can creates gaps between adjacent polygons.

--
Best regards,
Andrzej
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--
Felix Hartman - Openmtbmap.org & VeloMap.org

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Felix Hartman - Openmtbmap.org & VeloMap.org