[mkgmap-dev] Fix Sea Patch

Sun Feb 7 09:12:00 GMT 2021

Hi Gerd/Ticker,

Please find attached an updated patch that adds the --generate-sea=check option and fixes the other typo.

Cheers,
Mike

-----Original Message-----
From: Mike Baggaley [mailto:mike at tvage.co.uk] 
Sent: 31 January 2021 17:31
To: 'Development list for mkgmap' <mkgmap-dev at lists.mkgmap.org.uk>
Subject: RE: [mkgmap-dev] Fix Sea Patch

Hi Ticker,

The third case (water areas) will be because they are ordered in the wrong direction, so they are being picked up as land rather than water - hence the error message of land within land. There is no sea showing on the standard OSM renderer for way 255902449. This one is presumably seawater that gets refilled at extra high tide. My own generated map does show seawater at this point. I haven't checked the others.

I'll look at adding an option for checking the sea data (--generate-sea=check) and fix the typo you mentioned.

Cheers,
Mike

-----Original Message-----
From: Ticker Berkin [mailto:rwb-mkgmap at jagit.co.uk] 
Sent: 30 January 2021 17:05
To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
Subject: Re: [mkgmap-dev] Fix Sea Patch

Hi Mike & Gerd

I've just tried running with this on britain-and-ireland.osm.pbf using:
 --generate-sea=multipolygon,extend-sea-sectors,close-gaps=750

I got a few messages from it that I don't get normally - attached.

Looking at some of these, I found:
1/ islands, tagged with coastline, within lakes.
2/ strange inland coastline triangles (didn't check which way round the
coastline went) Source "OS_Opendata_Vectormap_District"
3/ water areas,
close to the sea - maybe salt-water lagoons, tagged with coastline -
I'm not sure why these are flagged if inland seas are allowed.

Some of these could be fixed in OSM.

The run-time has increases from about 35 mins to 44 mins (would need to
run again in a clean environment to be sure of this). I suggest having
an option to enable the extra checking.

I don't have any problem with more detailed logging.

Good to fix the spelling mistake (but should fix loadLandAndSee as
well)

Ticker

On Fri, 2021-01-29 at 11:18 +0000, Mike Baggaley wrote:
> Hi Gerd, attached is a slightly updated patch, with test data and the
> results from r4600 and the patch. The existing code does not identify
> all
> the problems in the test data and does not provide sufficiently
> detailed
> information on those it does find to enable investigation/correction.
> 
> The test data contains 4 test scenarios:
> land within sea within land, no errors - the existing code is ok here
> sea within land within sea, the outer sea should produce an error -
> the
> existing code is ok here
> land within land within land, the two inner lands should produce an
> error -
> these are not found by the existing code
> sea within sea within sea, all three seas should produce an error -
> the
> existing code finds the errors but does not identify the surrounding
> way for
> the inner two
> 
> Cheers,
> Mike
> 
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com] 
> Sent: 18 January 2021 11:54
> To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: Re: [mkgmap-dev] Fix Sea Patch
> 
> Hi Mike,
> 
> it would be great  to have some unit tests or at least a sample file
> containing the problem cases which are treated by your patch.
> 
> Gerd
> 
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Mike
> Baggaley <mike at tvage.co.uk>
> Gesendet: Montag, 18. Januar 2021 10:06
> An: 'Development list for mkgmap'
> Betreff: Re: [mkgmap-dev] Fix Sea Patch
> 
> Hi Gerd,
> 
> I had too little logging information in the version I sent
> previously. The
> attached remedies that.
> 
> Cheers,
> Mike
> 
> -----Original Message-----
> From: Mike Baggaley [mailto:mike at tvage.co.uk]
> Sent: 18 January 2021 00:28
> To: 'Development list for mkgmap' <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: RE: [mkgmap-dev] Fix Sea Patch
> 
> Hi Gerd,
> 
> I'm not sure that mkgmap should be prescriptive about where the input
> data
> comes from. However, I have produced an updated patch that reports on
> errors
> in the input data without providing any functionality to fix the
> problems.
> Please see the attached patch that is able to identify most problems
> in sea
> data.
> 
> Cheers,
> Mike
> 
> -----Original Message-----
> From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> Sent: 05 January 2021 08:40
> To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: Re: [mkgmap-dev] Fix Sea Patch
> 
> Hi Mike & Ticker,
> 
> I would not want to add code to mkgmap to fix problems which only
> occur in
> data that is produced by a 3rd party software. My understanding is
> that the
> "fixing" should happen in that 3rd party software, not in mkgmap.
> 
> Gerd
> 
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Mike
> Baggaley <mike at tvage.co.uk>
> Gesendet: Montag, 4. Januar 2021 20:40
> An: 'Development list for mkgmap'
> Betreff: Re: [mkgmap-dev] Fix Sea Patch
> 
> Hi Ticker,
> 
> I use coastline data that is generated from just line data and the
> algorithm
> used is not able to properly determine whether polygons are islands
> or
> water. It does however make sure polygons are closed, so I don't have
> problems with having to join ways together and hence I don't use
> close-gaps
> or extend sea-sectors.
> 
> I'm unclear exactly what an anti-island is supposed to be - I have
> considered it to be a separate bit of sea, and in my data I have lots
> of
> those that are correct. They are only incorrect if they are within
> the sea,
> rather than the land. For example, if there is a coast road with sea
> on both
> sides of it, I am likely to have a separate sea polygon within the
> land if
> its connection to the sea is under a bridge. The patch checks for sea
> within
> sea and land within land. It doesn't then go back and recursively
> check for
> nested problems - I suspect this would be quite an overhead.
> 
> The code is certainly not perfect, but does produce enormously
> improved
> results for me at least. I can still see at least one error in my
> map, but I
> think the remaining errors are tile boundary issues that are resolved
> differently on adjacent tiles. I am thinking of a small app to read
> the
> mkgmap log file and the coastline data, reversing whatever mkgmap
> says is
> wrong. By running mkgmap without splitter on just the coastline data
> I
> should be able to avoid any tile boundary problems.
> 
> Cheers,
> Mike
> 
> -----Original Message-----
> From: Ticker Berkin [mailto:rwb-mkgmap at jagit.co.uk]
> Sent: 04 January 2021 13:58
> To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
> Subject: Re: [mkgmap-dev] Fix Sea Patch
> 
> Hi Mike & Gerd
> 
> I always try to use the coastline data in the downloaded OSM map to
> generate the sea with option:
>   --generate-sea=multipolygon,extend-sea
> -sectors,close-gaps=750
> and have only ever had 1 problem with faulty
> coastline. In this case it wasn't a reversed section but a lake had
> been tagged with coastline, worse, in the wrong direction so it
> wasn't
> treated as an internal sea, rather an island, flipping the rest of
> the
> tile to sea.
> 
> I sometimes have problems with the continuation of the downloaded
> country's
> coastlines being cut off and ending up near the middle of tiles, but
> closer
> to the wrong edge or, when extended to the edge, they are in the same
> direction as an adjacent coastline, because the un-crossing is
> outside the
> downloaded area.
> 
> @Mike - Do you use --coastlinefile to circumvent this type of problem
> and is
> there an advantage to this over using --precomp-sea? The data seems
> to need
> a lot of correcting!
> 
> If arbitrary bits of coastline are in the wrong direction, should you
> have
> another phase, after joining in the same direction and removing
> anti/islands. Try to join against their direction and moving closed
> ways to
> an ambiguous closed list and other ways that joined to an ambiguous
> linear
> list. Then see if the ambiguous ones can be resolved, maybe by
> weighting by
> the direction of the majority.
> 
> I feel that some of your fixes of land/sea are too late in the flow
> of code,
> ie after generateSeaBackgound has been set.
> 
> It seems a reasonably assertion that all anti-islands are a mistake
> in the
> data. I think the only one is the Caspian Sea, which is unlikely to
> be fully
> contained in a tile.
> 
> checkIslands(), to do the full job, would need to look at the nesting
> of
> sea/land/sea... so, given above, I don't think it worthwhile.
> 
> In verifyHits(), I don't see where any changes that resolves
> "adjacent hits
> in same direction" are applied. The 'fix' could make it totally wrong
> rather
> than partially wrong. Looking for 3 in the same direction and
> reversing the
> middle one might be better.
> 
> As I said earlier, I've never had a problem where this type of fixing
> would
> be of any use.
> 
> The swapping between land and sea needs to do more than just re
> -tagging; the
> multi-polygon handling needs to be considered and also the fullArea
> of sea.
> 
> Ticker
> 
> On Sat, 2021-01-02 at 10:32 +0000, Gerd Petermann wrote:
> > Hi Mike,
> > 
> > > This was removed some time ago because it didn't work properly
> > Do you have a version number where this happened? I only know the
> > floodblocker option which is still evaluated in the source.
> > 
> > Gerd
> > 
> > 
> > ________________________________________
> > Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> > von Mike Baggaley <mike at tvage.co.uk>
> > Gesendet: Donnerstag, 31. Dezember 2020 16:17
> > An: 'Development list for mkgmap'
> > Betreff: [mkgmap-dev] Fix Sea Patch
> > 
> > Hi Gerd,
> > 
> > Mkgmap used to contain some code that attempted to correct
> > incorrect
> > sea and
> > land data where polygons were ordered in the wrong direction. This
> > was
> > removed some time ago because it didn't work properly. I have put
> > together
> > the attached patch that works much better and have been using it
> > for
> > some
> > time. With the sea data that I use, which contains quite a large
> > number of
> > incorrectly ordered polygons, it manages to correct every error it
> > finds. It
> > won't be able to fix really gross errors, but providing most of the
> > data is
> > correct it will produce good results.
> > 
> > Please review and commit if happy.
> > 
> > Cheers,
> > Mike
> > _______________________________________________
> > mkgmap-dev mailing list
> > mkgmap-dev at lists.mkgmap.org.uk
> > http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
> 
> 
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
> 
> 
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
-------------- next part --------------
A non-text attachment was scrubbed...
Name: sea4.patch
Type: application/octet-stream
Size: 11985 bytes
Desc: not available
URL: <http://www.mkgmap.org.uk/pipermail/mkgmap-dev/attachments/20210207/8515f7be/attachment.obj>