[mkgmap-dev] mkgmap splitter - Liechtenstein - horrible split if --polygon-file option used.

Wed Jun 23 12:12:02 BST 2021

Okay - well I ran splitter against all geofrabrik extracts that I am having
on my server (so nearly all - notably excluding DACH and Greater Britain
extract) - and wrote a script comparing the splits. Overall because of Asia
continent map it is better to use polygon-file. Seeing those huge
differences on Asia, australia-oceania, Italy, Africa, Japan and Brazil
I do feel splitter should be doing a bit better. Especially Asia
continent is hard to understand the huge huge difference.
In general for tiny countries - do not use it. Do not use it for German
Bundesländer. Do not use polygon-file for Italy. But do use it on
Australia-Oceania, Africa, Japan, Brazil, and Asia continent map.

Now I wonder - will this change in the future? So meaning I have to run
this assessment once a year? Usually the additional tiles are mostly tiny -
there is no reason for having them. If the split results in the same amount
of tiles no matter using --polygon-file or not - it is not listed
(overall 176 extracts). I put those countries with huge difference in bold.
26 splits are better not using --polygon-file. 30 splits are better using
--polygon-file. 906 tiles less for Asia continent shows that splitting Asia
without --polygon-file is a right mess. On the other hand for some tiny
countries like Lichtenstein or German Bundesländer, and Africa using a
--polygon-file from geofabrik created a way too many useless tiles.
cnt1 = using --polygon-file, cnt0=not using polygon-file for splitting.

"for montenegro do not use polygon-file - cnt1 = 2 cnt0 = 7"
"for france use polygon-file - cnt1 = 336 cnt0 = 332"
"for netherlands do not use polygon-file - cnt1 = 91 cnt0 = 92"
"for germany use polygon-file - cnt1 = 259 cnt0 = 258"
"for liechtenstein do not use polygon-file - cnt1 = 1 cnt0 = 6"
"for monaco do not use polygon-file - cnt1 = 1 cnt0 = 2"
"for slovenia do not use polygon-file - cnt1 = 27 cnt0 = 28"
"for ukraine use polygon-file - cnt1 = 62 cnt0 = 61"
"for norway use polygon-file - cnt1 = 128 cnt0 = 115"
"for switzerland do not use polygon-file - cnt1 = 29 cnt0 = 30"
"for poland use polygon-file - cnt1 = 133 cnt0 = 127"
"for sweden use polygon-file - cnt1 = 60 cnt0 = 54"
"for finland do not use polygon-file - cnt1 = 66 cnt0 = 85"
"for spain use polygon-file - cnt1 = 91 cnt0 = 89"
*"for italy do not use polygon-file - cnt1 = 155 cnt0 = 201" *
"for denmark use polygon-file - cnt1 = 33 cnt0 = 32"
"for andorra do not use polygon-file - cnt1 = 1 cnt0 = 4"
"for estonia use polygon-file - cnt1 = 9 cnt0 = 8"
"for saarland do not use polygon-file - cnt1 = 4 cnt0 = 16"
"for hamburg do not use polygon-file - cnt1 = 3 cnt0 = 12"
"for hessen do not use polygon-file - cnt1 = 17 cnt0 = 18"
"for niedersachsen do not use polygon-file - cnt1 = 26 cnt0 = 27"
"for baden-wuerttemberg use polygon-file - cnt1 = 38 cnt0 = 36"
"for nordrhein-westfalen do not use polygon-file - cnt1 = 56 cnt0 = 57"
"for bayern do not use polygon-file - cnt1 = 47 cnt0 = 48"
"for berlin do not use polygon-file - cnt1 = 5 cnt0 = 13"
*"for australia-oceania use polygon-file - cnt1 = 210 cnt0 = 110" *
"for south-america do not use polygon-file - cnt1 = 337 cnt0 = 339"
*"for africa do not use polygon-file - cnt1 = 673 cnt0 = 742" *
"for russia use polygon-file - cnt1 = 431 cnt0 = 409"
"for central-america use polygon-file - cnt1 = 61 cnt0 = 58"
"for morocco do not use polygon-file - cnt1 = 19 cnt0 = 32"
"for azerbaijan do not use polygon-file - cnt1 = 3 cnt0 = 4"
"for malaysia-singapore-brunei do not use polygon-file - cnt1 = 16 cnt0 =
17"
"for china use polygon-file - cnt1 = 106 cnt0 = 100"
"for india do not use polygon-file - cnt1 = 109 cnt0 = 110"
"for indonesia do not use polygon-file - cnt1 = 193 cnt0 = 198"
*"for japan use polygon-file - cnt1 = 196 cnt0 = 154*"
"for kazakhstan use polygon-file - cnt1 = 14 cnt0 = 13"
"for philippines use polygon-file - cnt1 = 53 cnt0 = 52"
"for afghanistan do not use polygon-file - cnt1 = 12 cnt0 = 21"
"for myanmar use polygon-file - cnt1 = 18 cnt0 = 17"
"for australia use polygon-file - cnt1 = 68 cnt0 = 67"
"for new-zealand do not use polygon-file - cnt1 = 27 cnt0 = 28"
"for argentina use polygon-file - cnt1 = 33 cnt0 = 27"
*"for brazil use polygon-file - cnt1 = 265 cnt0 = 177" *
"for peru use polygon-file - cnt1 = 22 cnt0 = 21"
"for canada use polygon-file - cnt1 = 299 cnt0 = 275"
"for us-midwest use polygon-file - cnt1 = 155 cnt0 = 154"
"for us-pacific use polygon-file - cnt1 = 21 cnt0 = 18"
"for us-south use polygon-file - cnt1 = 265 cnt0 = 262"
"for us-west use polygon-file - cnt1 = 240 cnt0 = 226"
"for greenland use polygon-file - cnt1 = 4 cnt0 = 2"
"for mexico use polygon-file - cnt1 = 44 cnt0 = 43"
"for reunion do not use polygon-file - cnt1 = 3 cnt0 = 5"
*"for asia use polygon-file - cnt1 = 2489 cnt0 = 1505" *

On Sun, 20 Jun 2021 at 19:12, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

> Hi Felix,
>
> it tries to reduce the area that is outside the polygon. I think for most
> countries there is no good reason to use a polygon.
> Candidates are those which cross 180° and maybe those which have lots of
> unrelateed coastline inside the bounding box.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Felix Hartmann <extremecarver at gmail.com>
> Gesendet: Sonntag, 20. Juni 2021 15:12
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] mkgmap splitter - Liechtenstein - horrible split
> if --polygon-file option used.
>
> But why is it splitting up into so many parts?
> So that means you kinda have to check for every country individually if
> using poly or nor gives the split with less tiles? I would just prefer the
> split using less tiles so best I write a script to test that for every
> single country?
>
> On Sun, 20 Jun 2021, 15:27 Gerd Petermann <gpetermann_muenchen at hotmail.com
> <mailto:gpetermann_muenchen at hotmail.com>> wrote:
> Hi Felix,
>
> the polygon-file tells splitter that you don't want the rectangular bounds
> given in the *.osm file.
> This means you don't want the areas outside of the polygon. If you are
> happy with the result without polygon file just don't use it
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk<mailto:
> mkgmap-dev-bounces at lists.mkgmap.org.uk>> im Auftrag von Felix Hartmann <
> extremecarver at gmail.com<mailto:extremecarver at gmail.com>>
> Gesendet: Sonntag, 20. Juni 2021 10:17
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] mkgmap splitter - Liechtenstein - horrible split
> if --polygon-file option used.
>
> I think this applies to all "countries" / areas that are so small that
> they do not need a split or would split into very few areas. Another
> example is Monaco (2 tiles instead of 1 tile). For "countries" that are 10
> tiles or more anyhow - I did not find this problem.
>
> On Sun, 20 Jun 2021 at 11:08, Felix Hartmann <extremecarver at gmail.com
> <mailto:extremecarver at gmail.com><mailto:extremecarver at gmail.com<mailto:
> extremecarver at gmail.com>>> wrote:
> After last week looking at australia-oceania which was not splitted well
> without polygon-file - I now noticed that several small countries are split
> into way too many small tiles IF using .poly boundary file.
>
> I guess there is some bug? This tile should not be split at all - as the
> node count fits into 1 tile!
>
>
> Attached the splitter.log both with and without .poly file.
>
> --
> Felix Hartman - Openmtbmap.org & VeloMap.org
>
>
>
> --
> Felix Hartman - Openmtbmap.org & VeloMap.org
>
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>

-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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