[mkgmap-dev] Squaring off of land outlines

Tue Jan 28 22:52:51 GMT 2020

Performance of map on device is drastically improved you you kick out those
tiny polygons. Especially in cities where people have detail mapped all
buildings. If you don't have building=yes or building=* in your style -
then you can likely live with the filter disabled (not sure how much bigger
the map data gets).

On Tue, 28 Jan 2020 at 21:41, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

> Hi Mike,
>
> "sea" is build from shapes (= polygons).
> The size filter is not explained in the style manual, but in the options
> --min-size-polygon and --polygon-size-limits.
> Unfortunately the filter works a bit unpredictable at low resolutions, so
> in my eyes it is a good idea to disable.
> I've never fully understood the purpose of this filter. I think it should
> improve performance, but it seems to decrease quality even more.
>
> You may play with --min-size-polygon=0 to see what happens when the filter
> is disabled.
>
> Gerd
>
> ________________________________________
> Von: Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Dienstag, 28. Januar 2020 21:21
> An: 'Gerd Petermann'; 'Development list for mkgmap'
> Betreff: RE: [mkgmap-dev] Squaring off of land outlines
>
> Brilliant! A big improvement! It still doesn't exactly match the land
> polygon, but that doesn't matter for my purposes. I suggest changing the to
> do list so it says use the same algorithm for shapes, lines and sea. I also
> suggest adding a sentence to the style manual in the explanation of
> mkgmap:skipSizeFilter - the description doesn't explain the purpose or what
> the effect is of passing the size filter.
>
> Thanks for your assistance,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 28 January 2020 19:03
> To: Mike Baggaley <mike at tvage.co.uk>
> Subject: AW: [mkgmap-dev] Squaring off of land outlines
>
> Hi Mike,
>
> some small rather small sea polygons are filter by the size filter.
> Change the statememnt for sea polygons to this:
> natural=sea {add mkgmap:skipSizeFilter=true; name '${name}'} [0x32
> resolution 14]
>
> See also the corresponding rule in the default style:
> natural=sea {add mkgmap:skipSizeFilter=true; set mkgmap:drawLevel=2} [0x32
> resolution 10]
>
> Gerd
>
> ________________________________________
> Von: Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Dienstag, 28. Januar 2020 19:39
> An: 'Gerd Petermann'
> Betreff: RE: [mkgmap-dev] Squaring off of land outlines
>
> Thanks Gerd. I has been considering trying to find the problem myself, but
> I'm not familiar with the writing sections of code, and they are
> complicated
> to get to grips with.
>
> Cheers,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 28 January 2020 16:16
> To: Mike Baggaley <mike at tvage.co.uk>; 'Development list for mkgmap'
> <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: AW: [mkgmap-dev] Squaring off of land outlines
>
> Hi Mike,
>
> okay, I'll have a closer look now.
>
> Gerd
>
> ________________________________________
> Von: Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Dienstag, 28. Januar 2020 16:51
> An: 'Gerd Petermann'; 'Development list for mkgmap'
> Betreff: RE: [mkgmap-dev] Squaring off of land outlines
>
> Hi Gerd, the problem I have is not the one in the to do list. If I add the
> polygon fill for natural=coastline, this does produce a different outline
> than the one for the line, but both are reasonable approximations and
> neither contains unexpected artefacts. The sea generation approximation is
> wildly different and contains unwanted artefacts.  Please see the attached
> image that contains land in brown, sea in blue and an area of white that is
> not filled by either. I believe this is a bug in the sea generation code. I
> would expect sea generation to use the same algorithm as for filled areas
> so
> that holes are not left. I'm not too worried about the line being slightly
> different.
>
> Regards,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 28 January 2020 14:59
> To: Mike Baggaley <mike at tvage.co.uk>; 'Development list for mkgmap'
> <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: AW: [mkgmap-dev] Squaring off of land outlines
>
> Hi Mike,
>
> See last point in the todo list: http://www.mkgmap.org.uk/dev/todo
> I think what you see is exactly the result of the two different algos.
> I can only suggest to omit the rendering of polygon outlines at resolutions
> below 24.
>
> ________________________________________
> Von: Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Dienstag, 28. Januar 2020 15:23
> An: 'Gerd Petermann'; 'Development list for mkgmap'
> Betreff: RE: [mkgmap-dev] Squaring off of land outlines
>
> Hi Gerd, I have produced a small sample which demonstrates the problem. It
> contains one very small island. I have cut down the style to a bare minimum
> with just two resolutions: 24 and 14 containing just sea and a coastline
> outline. At resolution 24 the sea and coastline are coincident. At 14, they
> are wildly different. The coastline at low resolution includes a spur which
> is a complication. The ideal sea boundary would be the same as the
> coastline, but with the spur removed (or perhaps the spur should not be on
> the coastline either). I have included the style, typ file, command line in
> a batch file and osm data in the attached zip. Please let me know if you
> need anything else.
>
> Cheers,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 28 January 2020 08:26
> To: Mike Baggaley <mike at tvage.co.uk>; 'Development list for mkgmap'
> <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: AW: [mkgmap-dev] Squaring off of land outlines
>
> Hi Mike,
>
> I can try to find out what's wrong but I would need a lot more details
> about
> your map creation process. Could be an error in mkgmap or in the OSM data
> or
> in the --levels option or in the --min-size-polygon option or
> --polygon-size-limits or ...
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Mike
> Baggaley <mike at tvage.co.uk>
> Gesendet: Montag, 27. Januar 2020 19:07
> An: 'Development list for mkgmap'
> Betreff: Re: [mkgmap-dev] Squaring off of land outlines
>
> HI Gerd, I don't have an old map, but this has been happening for some time
> - I am not sure whether it has always done this, but thought it would be
> worth trying a few old versions to see whether it is bug that got
> introduced, or is one that has always been there. It looks similar to the
> problem reported on Feb 18 2017 with "Terraced/pixellated coastline with
> --precomp-sea" as the title. I am not using --precomp-sea, but the problem
> I
> am getting is also in the sea outline. NopMap indicated that his problem
> was
> fixed in r3819, however, I have downloaded the source to that version and
> compiled it, and it exhibits the same problem for me.
>
> Regards,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 27 January 2020 08:36
> To: 'Development list for mkgmap' <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: Re: [mkgmap-dev] Squaring off of land outlines
>
> Hi Mike,
>
> I am not aware of a folder that keeps all older releases or an error that
> would be related to this.
> Are you sure that you didn't change mgkmap options like --levels or the
> style or the typ file?
> Do you still have a map which looks better? In that case you should find
> the
> string mkgmap in the img file, e.g. "mkgmap-r4431"
>
> Gerd
>
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Mike
> Baggaley <mike at tvage.co.uk>
> Gesendet: Montag, 27. Januar 2020 01:43
> An: 'Development list for mkgmap'
> Betreff: [mkgmap-dev] Squaring off of land outlines
>
> Hello,
>
> I am getting squaring off of the outline between land and sea at low zoom
> levels (less than 16) - see attached BaseCamp images of Gran Canaria at
> resolution 16 and at resolution 14 displayed at the same size. Obviously
> some reduction in accuracy is expected at lower zoom level, but not these
> artefacts. I'm not sure when this started happening but believe it was some
> time ago. I can't seem to find the old releases to try previous versions,
> http://svn.mkgmap.org.uk/mkgmap/releases/ just shows me an empty folder.
> Can
> you point me to the correct download folder that contains the previous jar
> files, and/or let me know if this is a known problem, and if so whether
> there is a workaround?
>
> Thanks,
> Mike
>
>
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>
>
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-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
Schusterbergweg 32/8
6020 Innsbruck
Austria - Österreich
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