[mkgmap-dev] mkgmap ToDo list

Tue Apr 29 19:48:24 BST 2014

I don't have the number for Germany, but perhaps the world suffices?

The image size distribution of my generic map is:
<2MB   some
2-3MB  260
3-4MB  410
4-5MB  600
5-6MB  580
6-7MB  390
7-8MB  250

On 2014-04-29 20:37, Gerd Petermann wrote:
> Hi Lambertus,
> 
> okay, if I got that right you finally get *.img files with a size
> near (but below) 8MB, so maybe Henning can use that script, too.
> 
> If you do that for e.g. Germany, how small is tpically the smallest
> *.img file ?
> Is it probably near 4 MB?
> 
> Gerd
> 
>> To: mkgmap-dev at lists.mkgmap.org.uk
>> Date: Tue, 29 Apr 2014 20:30:27 +0200
>> From: osm at na1400.info
>> Subject: Re: [mkgmap-dev] mkgmap ToDo list
>> 
>> These are the direct results from Splitter. The format is o5m, both
>> input as output. Splitter version is: r321.
>> 
>> For this test I split the original source with --max-nodes=8000000.
> Then
>> I render the initial tiles, when the result is larger than 8MB it's
>> subsplit again with --max-nodes=(8000000-(attempt*100000)). The
> initial
>> source files are ~70MB (o5m) and after several subsplits the two
> *.img
>> are < 8MB. During this process --max-nodes has been reduced to e.g.
>> 7500000 and the source file is split up in two o5m files of about
> 37MB.
>> 
>> I can upload an example source file and it's two subsplit siblings
> if
>> you want.
>> 
>> 
>> On 2014-04-29 19:38, GerdP wrote:
>> > Hi Lambertus,
>> >
>> > that's interesting. Are these the img file sizes or the osm file
> sizes?
>> >
>> > Gerd
>> >
>> >
>> > Lambertus wrote
>> >> Unfortunately I cannot confirm that. Below is a bit of logging
> from my
>> >> script:
>> >> Original: 97000020 (70551453), New: 0 (35684445), New: 1
> (36852845)
>> >> Original: 97000001 (74621042), New: 0 (37522992), New: 1
> (37222739)
>> >> Original: 97000002 (73391358), New: 0 (37679505), New: 1
> (38098627)
>> >> Original: 97000003 (77862567), New: 0 (39075311), New: 1
> (39261197)
>> >>
>> >> The original files above contain contour data, the filesize is
> between
>> >> brackets. As you can see both resulting file are approximately
> the
>> >> same
>> >> size.
>> >>
>> >> On 2014-04-29 15:39, Gerd Petermann wrote:
>> >>> Hi Lambertus,
>> >>>
>> >>> and I guess that even after this optimization you will
>> >>> see a factor 3 or higher between the largest tile and the
> smallest.
>> >>> Can you confirm that?
>> >>>
>> >>> Gerd
>> >>>
>> >>>> Date: Tue, 29 Apr 2014 15:32:38 +0200
>> >>>> From:
>> >
>> >> osm@
>> >
>> >>>> To:
>> >
>> >> mkgmap-dev at .org
>> >
>> >>>> Subject: Re: [mkgmap-dev] mkgmap ToDo list
>> >>>>
>> >>>> Num-tiles=x would indeed be better for this specific need.
>> >>>>
>> >>>> It is my experience that it regularly takes multiple calls to
>> >>> Splitter
>> >>>> to get 2+ sub-tiles when you reduce the max-nodes by 100k for
> each
>> >>>> sub-split attempt. This is what I currently do to get an
> optimum in
>> >>>> tile-size vs total number of tiles.
>> >>>>
>> >>>>
>> >>>>
>> >>>> On 29/04/2014 15:09, Gerd Petermann wrote:
>> >>>> > Hi Lambertus,
>> >>>> >
>> >>>> > that sounds like a possible change in splitter:
>> >>>> > Instead of specifying max-nodes you may specify --num-tiles=x
>> >>>> > and splitter will try to find a split that produces excactly
> x
>> >>> tiles
>> >>>> > which are not too narrow and have a node number which is not
>> >>>> > too far from the average (but still aligned to a multiple of
> map
>> >>> units
>> >>>> > as now).
>> >>>> > So, for your script that means you don't have to find the
>> >>> max-nodes
>> >>>> > value.
>> >>>> >
>> >>>> > I'll think about this again...
>> >>>> >
>> >>>> > Gerd
>> >>>> >
>> >>>> > > Date: Tue, 29 Apr 2014 14:59:36 +0200
>> >>>> > > From:
>> >
>> >> osm@
>> >
>> >>>> > > To:
>> >
>> >> mkgmap-dev at .org
>> >
>> >>>> > > Subject: Re: [mkgmap-dev] mkgmap ToDo list
>> >>>> > >
>> >>>> > > While this possibly can be solved in Splitter or Mkgmap, it
>> >>> could also
>> >>>> > > be solved by your build-script when you add a maximum tile
> size
>> >>> check
>> >>>> > > and re-split (with a lower number of max-nodes) until you
> get
>> >>> two or
>> >>>> > > more sub-tiles. Granted, this adds complexity to the script
> but
>> >>> it works
>> >>>> > > well for me.
>> >>>> > >
>> >>>> > > On 25/04/2014 21:54, Henning Scholland wrote:
>> >>>> > > > Hi Gerd,
>> >>>> > > >
>> >>>> > > > I would like to have img-tiles which have globally nearly
> the
>> >>> same
>> >>>> > > > filesize, so that they use the space of devices like
> eTrex 10.
>> >>>> > > >
>> >>>> > > > With my actual map I use globally the same value for
>> >>> max-nodes. But the
>> >>>> > > > size of the img-tiles differ more then factor 2. Eg. a
> tile in
>> >>> Germany
>> >>>> > > > is between 2 and 5 mb where a tile in China is about 10
> mb. If
>> >>> I remove
>> >>>> > > > details, this difference will increase, because in
> Germany
>> >>> more objects
>> >>>> > > > will be removed from the img-tile then in China.
>> >>>> > > >
>> >>>> > > > Henning
>> >>>> > > >
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