[mkgmap-dev] Similar Arcs

Mon May 24 14:15:34 BST 2021

I thought that patch could be used to remove the dual highways at low
resolutions. Does not seem to work for that with a value of 4... So it is
only about routing, right? I will not work on lines but only roads?

On Sun, 23 May 2021 at 20:02, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

> Hi Mike,
>
> the NodCheck (and NodDisplay is part of the display utility, see
> https://svn.mkgmap.org.uk/svn/display
> NodCheck reports lots of errors about angles and lengths of arcs which
> probably are not critical and mostly caused by rounding.
>
> There are some pdf docs about the IMG format and also the wiki
> https://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin/NOD_Subfile_Format
> Some details are probably not documented, esp. the last findings about
> encoding of bearings.
>
> I think it is possible to suppress some duplicate arcs, e.g. if two roads
> have the same first arc it should be possible to truncate one of the roads.
> It might be needed to remove all the data in RGN and NET as well, so that
> you simulate the removal of data in OSM. I don't see a need for this, the
> effect should be very small for styles which don't try to make objects like
> amenity=parking routable.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Sonntag, 23. Mai 2021 19:27
> An: 'Development list for mkgmap'
> Betreff: Re: [mkgmap-dev] Similar Arcs
>
> Hi Gerd,
>
> The primary reason for the patch and hence the rules is to reduce the
> number
> of similar arcs warnings to a manageable number that are actually useful. A
> useful side effect is slightly reducing the size of the map. Many of the
> warnings are caused by highway areas overlapping linear highways. You are
> right that the patch does cause incorrect routing data - the first few I
> tried to route over seemed to be OK, but others failed, so I assume it is
> just luck when one still works. I can't find any NodCheck in the code, and
> with all warnings enabled, I don't see any messages relating to this. I was
> following your suggestion about using the code for --report-similar-arcs as
> a base to drop overlapping arcs. Checking back, I see you did mention you
> didn't know whether this would produce incorrect NOD data. I have realised
> I
> also need to delete the reverse arc and have added code for that, but
> haven't discovered how the NOD data is connected. Can you point me in the
> right direction? Don't suppose there is any documentation about the code
> structure...
>
> Cheers,
> Mike
>
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 22 May 2021 06:31
> To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: Re: [mkgmap-dev] Similar Arcs
>
> Hi Mike,
>
> what exactly is the benefit of those rules? What's the problem if the
> similar arcs are not removed?
> I can't belief that this works without causing possibly wrong routing data.
> Doesn't NodCheck complain about the removed arcs?
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Mike
> Baggaley <mike at tvage.co.uk>
> Gesendet: Samstag, 22. Mai 2021 00:51
> An: 'Development list for mkgmap'
> Betreff: [mkgmap-dev] Similar Arcs
>
> Hi Gerd,
>
> Please find attached the patch for deleting similar arcs. It uses a new
> mkgmap:nooverlap tag which can be set to a number between 0 and 127
> (default
> 0) in the lines file. If set to a number greater than zero then the
> overlapping part of the line will be deleted if it overlaps another line,
> providing the access of the other line is a superset of its access. If both
> lines have non zero values and have the same access then the line with the
> higher value will be deleted.
>
> In my style file I have the following:
>
> highway=service & (area=yes | mkgmap:mp_created=true) & (foot=yes |
> foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* |
> access=yes | access=permissive))) {set mkgmap:car=no; set
> mkgmap:bicycle=no;
> set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set
> mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none;
> set mkgmap:nooverlap=1} [0x13 road_class=0 road_speed=0 resolution 22]
>
> highway=pedestrian & (area=yes | mkgmap:mp_created=true) & (foot=yes |
> foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* |
> access=yes | access=permissive))) {set mkgmap:car=no; set
> mkgmap:bicycle=no;
> set foot=yes; set mkgmap:flare-check=no; set mkgmap:numbers=false; set
> mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none;
> set mkgmap:nooverlap=1} [0x0d road_class=0 road_speed=0 resolution 22]
>
> amenity=parking & (parking!=* | parking=surface) & (foot=yes |
> foot=designated | foot=official | foot=permissive | (foot!=* & (access!=* |
> access=yes | access=permissive))) {set mkgmap:car=no; set
> mkgmap:bicycle=no;
> set foot=yes; set mkgmap:numbers=false; set
> mkgmap:set_unconnected_type=none; set mkgmap:set_semi_connected_type=none;
> set mkgmap:nooverlap=2; set mkgmap:delivery=no; set mkgmap:truck=no; set
> mkgmap:bus=no; set mkgmap:taxi=no; set mkgmap:emergency=no } [0x08
> road_class=0 road_speed=0 resolution 24 continue]
>
> and similar for railway=platform, man_made=pier, man_made=jetty and
> leisure=slipway.
>
> Cheers,
> Mike
>
>
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-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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