new option --add-boundary-nodes-at-admin-boundaries

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new option --add-boundary-nodes-at-admin-boundaries

Gerd Petermann
Hi all,

please try r4213 in the country-border branch, I think it is ready for merge into trunk:
http://www.mkgmap.org.uk/download/mkgmap.html

I hope this description is clear enough, please suggest improvements / corrections:

--add-boundary-nodes-at-admin-boundaries=NUM
        This option controls how mkgmap calculates special routing nodes which
        are needed by Garmin software to allow routing between different map tiles.
        These nodes are written to section 3 and 4 in the NOD file.
        When a road crosses the tile boundary (bbox), the road is split at this
        point and such a special node is written. This allows routing between
        one set of tiles produced by splitter.jar. However, if you create a map
        from different sets of tiles, those tiles are likely to overlap.
        For the overlapping tiles, none of the entries in NOD3 match and thus
        routing across tile border doesn't work when the route is not fully
        covered by one of the tiles.
        The option tells mkgmap to add special nodes whereever a road touches or
        crosses an administratve boundary. The NUM parameter specifies a filter
        for the admin_level. Boundaries with a higher admin_level value are ignored.
        The default value is 2 (country borders). Another reasonable value might
        be 4. A value less or equal to 0 tells mkgmap to ignore intersections at
        administrative boundaries.  

Gerd
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Re: new option --add-boundary-nodes-at-admin-boundaries

Greg Troxel-2

Gerd Petermann <[hidden email]> writes:

> please try r4213 in the country-border branch, I think it is ready for merge into trunk:
> http://www.mkgmap.org.uk/download/mkgmap.html
>
> I hope this description is clear enough, please suggest improvements / corrections:

My usual plea about mkgmap: the options that are recommended should be
on by default, instead of expecting the user to enable 20 different
options after understanding them.

If you mean to add the code with it off, and after testing that it
doesn't cause harm, make it default, then I withdraw my complaint :-)
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Re: new option --add-boundary-nodes-at-admin-boundaries

Gerd Petermann
Hi Greg,

seems the description is not clear enough. The default of this option is "2", that means it is switched on by default.
It has no effect unless --route is also on.

Gerd

________________________________________
Von: Greg Troxel <[hidden email]>
Gesendet: Mittwoch, 1. August 2018 00:22
An: Gerd Petermann
Cc: [hidden email]
Betreff: Re: [mkgmap-dev] new option --add-boundary-nodes-at-admin-boundaries


Gerd Petermann <[hidden email]> writes:

> please try r4213 in the country-border branch, I think it is ready for merge into trunk:
> http://www.mkgmap.org.uk/download/mkgmap.html
>
> I hope this description is clear enough, please suggest improvements / corrections:

My usual plea about mkgmap: the options that are recommended should be
on by default, instead of expecting the user to enable 20 different
options after understanding them.

If you mean to add the code with it off, and after testing that it
doesn't cause harm, make it default, then I withdraw my complaint :-)
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Re: new option --add-boundary-nodes-at-admin-boundaries

Greg Troxel-2


Gerd Petermann <[hidden email]> writes:

> seems the description is not clear enough. The default of this option
> is "2", that means it is switched on by default.  It has no effect
> unless --route is also on.

Thanks.  Having it on by default if --route is on sounds good.

(Separately, I wonder why --route isn't default.  Does anybody really
want a non-routable map these days?  But that's a separate, very old
question.)

I am glad to see this option.  I have been avoiding the issue by using
the geofrabrik US northeast option.  I wonder if it should be using
states (admin=4) in addition, in the US.

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Re: new option --add-boundary-nodes-at-admin-boundaries

Gerd Petermann
Hi Greg,

my understanding is this:
The additional nodes (only) help when you create multiple maps. For example,
if you have a script that creates a map for a given geofabrik extract by executing splitter and mkgmap.
If you feed that script 1st with Maine and 2nd with New Hampshire you get two different maps
with overlapping tiles.
If you use osmconvert to merge the two extracts before using the script there are no overlapping tiles and
thus there is no need for the additional nodes.

Gerd

________________________________________
Von: Greg Troxel <[hidden email]>
Gesendet: Mittwoch, 1. August 2018 12:36
An: Gerd Petermann
Cc: [hidden email]
Betreff: Re: AW: [mkgmap-dev] new option --add-boundary-nodes-at-admin-boundaries



Gerd Petermann <[hidden email]> writes:

> seems the description is not clear enough. The default of this option
> is "2", that means it is switched on by default.  It has no effect
> unless --route is also on.

Thanks.  Having it on by default if --route is on sounds good.

(Separately, I wonder why --route isn't default.  Does anybody really
want a non-routable map these days?  But that's a separate, very old
question.)

I am glad to see this option.  I have been avoiding the issue by using
the geofrabrik US northeast option.  I wonder if it should be using
states (admin=4) in addition, in the US.

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Re: new option --add-boundary-nodes-at-admin-boundaries

Greg Troxel-2

Gerd Petermann <[hidden email]> writes:

> my understanding is this:
> The additional nodes (only) help when you create multiple maps. For example,
> if you have a script that creates a map for a given geofabrik extract by executing splitter and mkgmap.
> If you feed that script 1st with Maine and 2nd with New Hampshire you get two different maps
> with overlapping tiles.
> If you use osmconvert to merge the two extracts before using the script there are no overlapping tiles and
> thus there is no need for the additional nodes.

Thanks - that matches my understanding too.  What I meant is that long
long ago I was using multiple state extracts, and I think feeding them
into splitter together, and I found that I could not make cross-state
routes.  But that may work now because of geofrabrik itself being sure
to have matching nodes in adjacent extracts.

Based on that trouble, when us-northeast came out, I started using it,
since it was only 600 MB or so for the img, which was small enough not
to be a hassle.

I was thinking that it might be reasonable to process each US state to
produce an img, separately, and then to just load the ones you want.  So
people may want to try that out with
  --add-boundary-nodes-at-admin-boundaries=4
in the US.
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