[mkgmap-dev] Duplicate cities

Fri May 22 08:34:04 BST 2015

Hi Colin,

it turned out that your concerns were okay,
the differences in the UK are much higher,
so I've implemented a new option wanted-admin-level.

See also post for splitter 423.

Gerd

From: gpetermann_muenchen at hotmail.com
To: mkgmap-dev at lists.mkgmap.org.uk
Date: Thu, 21 May 2015 18:56:46 +0200
Subject: Re: [mkgmap-dev] Duplicate cities

Hi Colin,

It would not be complicated to implement, but I fear the documentation.
Today I've tested with Brazil, once with levels 4-11, once with 5-11.
Size difference was only 10MB (sum for all 27 tiles), 
so I don't expect a big change in the UK
when you would use e.g. 6-11.

I'll think about a good option name and docu for it,
if I find one I'll add it.
Suggestions are wellcome.

Gerd

Date: Thu, 21 May 2015 18:44:32 +0200
From: colin.smale at xs4all.nl
To: mkgmap-dev at lists.mkgmap.org.uk
Subject: Re: [mkgmap-dev] Duplicate cities

Well, I am thinking that the whole of the boundary of Scotland for example (level 5 is the region, level 4 is the nation - they are coterminous) will add an enormous overhead to all the tiles in Scotland. Maybe it isn't worth it, especially if you say it is complex to implement.

As an aside, what happens to tiles which are entirely enclosed by a boundary, without there being a node within the tile?

//colin

On 2015-05-21 18:31, Gerd Petermann wrote:

Hi Colin,

what difference do you expect when you 
are able to configure that value?
I'd expect a few MB difference in the OSM file size
and nearly no difference in mkgmap output,
on the other hand it woud be another complicated
option.

Gerd

Date: Thu, 21 May 2015 18:25:12 +0200
From: colin.smale at xs4all.nl
To: mkgmap-dev at lists.mkgmap.org.uk
Subject: Re: [mkgmap-dev] Duplicate cities

 Could the admin_levels be made configurable in some way? There are considerable differences in the size of these areas between different countries. I am thinking particularly of the lower admin_level (5) which might be better set to 6 (or even 8) in the UK. Level 5 corresponds to "regions" which are basically only for statistics and some government stuff - not many people would know what region they are in (except they could probably guess because they are called things like "South East England"). Level 6 corresponds to Counties, and everyone uses them.
 //colin

On 2015-05-21 17:00, Gerd Petermann wrote:

Hi Andrzej,

I tried using --boundary-tags=administrative        
for splitter, the amount of additional data depends
on the size of the largest boundaries.

Attached is a small patch that changes splitter so
that it keeps administrative boundaries complete
when the admin_level is between 5 and 11 (including).

This doesn't add much data to the output files
in comparison to --boundary-tags=administrative        
when splitting e.g. Brazil with --max-nodes=800000
and --output=o5m:
a) r422 output size: ~ 359 M 
b) patched version : ~381 M 
c) unpatched r422 with  --boundary-tags=administrative: 402 M

I've also tested the effect on mkgmap.
As expected, version a) produces some wrong / duplicate POI,
but I don't see them for b) or c).
The throughput is nearly identical, and the final img size is also almost equal.

So, I think the patch is the best compromise.

Gerd

> Date: Thu, 21 May 2015 12:56:43 +0200
> From: popej at poczta.onet.pl
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] Duplicate cities
> 
> Hi Gerd,
> 
> > Hmm, splitter keeps most mp-relations complete, we only
> > exclude some boundary relations.
> 
> I see. But maybe potential increase wouldn't be that big, if you add 
> boundaries?
> 
> Or maybe you can preserve only some levels of boundaries?
> 
> Or you can use boundary data form --bounds option?
> 
> Anyway, I prefer version 1 - keep complete relation, that could be 
> useful for mkgmap.
> 
> -- 
> Best regards,
> Andrzej
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev

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