[mkgmap-dev] mkgmap ToDo list

Tue Apr 29 19:37:35 BST 2014

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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