[mkgmap-dev] precompiled sea

Thu Jan 30 08:10:26 GMT 2020

Hi Mike,

quite a lot of missunderstandings ;)
1) The data in land-polygons-split-4326.zip is calculated (compiled) from OSM coastline data. AFAIK the same data is used by the renderer of https://www.openstreetmap.org
Find more details  here https://osmdata.openstreetmap.de/data/land-polygons.html
The expected avantage is that the coastline data produced by them is complete and correct (no gaps, no reversed coastline)
2) The data in sea.zip uses the OSM pbf format. It containes the result of processing this (hopefully correct) data using the algorithm that is used with --generate-sea=multipolygon. That's also a reason why it is called pre-compiled.
3) You should load the data of a rather small sea*.pbf file into JOSM to sea what it contains. You'll sea the result of "cutting out holes(islands) of a multipolygon".
So, the file contains only simple ways, no multipolygons.

If you don't want or cannot use precompiled sea data you should try the sub options of --generate-sea.

Gerd
PS: See also my trick regarding testing sea: http://gis.19327.n8.nabble.com/precomp-sea-problem-tp5953261p5953281.html

________________________________________
Von: Mike Baggaley <mike at tvage.co.uk>
Gesendet: Donnerstag, 30. Januar 2020 00:24
An: 'Gerd Petermann'; 'Development list for mkgmap'
Betreff: RE: [mkgmap-dev] precompiled sea

Hi Gerd, having now read your link on generating sea yourself, I gather that
mkgmap cannot produce precompiled sea from OSM files, only from ESRI files.
I also wasn't aware that optional code had to be included to use the sea
generator. I could include the optional code in my mkgmap build, but it
looks like using precompiled sea is a non-starter for me if it can't read
OSM data. The original source of my land/sea border was ESRI, but this data
has gone through a filtering process and been converted to OSM format.

I had assumed that the precompiled sea tiles were in img format, but from
opening the precompiled sea zip file from the download page, I see the files
are pbf, suggesting that 'precompiled' is something of a misnomer if they
are just OSM files. I assume it refers to converting from ESRI to OSM, which
I don't need, as it looks like it is doing something pretty similar to what
I already have.

Ah well, back to the drawing board...

Cheers,
Mike

-----Original Message-----
From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
Sent: 29 January 2020 20:12
To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
Subject: Re: [mkgmap-dev] precompiled sea

Hi Mike,

if you want to compile your own  sea.zip see
https://wiki.openstreetmap.org/wiki/Mkgmap/help/options#Using_precompiled_se
a

If you want to create a map similar to that created with
java -jar mkgmap.jar  --generate-sea=multipolygon
--style-file=styles\coastline -c template.args
you have to use something like
java -jar mkgmap.jar --precomp-sea=\osm\sea.zip
--style-file=styles\coastline -c template.args

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd
Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Mittwoch, 29. Januar 2020 20:22
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] precompiled sea

Hi Mike,

not sure what you are trying to do. What do you expect to get with the last
command?

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Mike
Baggaley <mike at tvage.co.uk>
Gesendet: Mittwoch, 29. Januar 2020 19:20
An: 'Development list for mkgmap'
Betreff: [mkgmap-dev] precompiled sea

Hi, I have not used precomp sea before and am struggling to compile the sea
tiles. Using the following process I get a map with no sea:

Used osmfilter to extract just the coastline data
Used splitter on the coastline data
Used mkgmap on the splitter data with a simple style that just processes
coastline and with --generate-sea=multipolygon. I can see some img files
created in my sea folder
Used splitter again on the original data
Used mkgmap again with --precomp-sea and --generate-sea=multipolygon

Am I doing something wrong?

Regards,
Mike

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