June 2021 - mkgmap-dev - The mkgmap lists

Error in splitter reg. concave polygons
by Gerd Petermann 24 Jun '21

24 Jun '21

Hi all, there is a bug reg. the handling of polygons (given with options --polygon-file or --polygon-desc-file) when a polygon is concave. splitter uses the given polygon to create a rastered version. The raster elements are determined by the resolution. In some cases it happens that the rastered version has holes while the original shape doesn't have them. If that happens and splitter is not executed with -ea the result will be garbage, with -ea splitter crashes. Happens e.g. for attached niedersachsen.poly while the modifed version works fine. I have a fix for that but it needs some more testing. Gerd

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mkgmap splitter - Liechtenstein - horrible split if --polygon-file option used.
by Felix Hartmann 23 Jun '21

23 Jun '21

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

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Commit r4786: merge from low-res-opt branch
by svn commit 23 Jun '21

23 Jun '21

Version mkgmap-r4786 was committed by gerd on Wed, 23 Jun 2021 merge from low-res-opt branch - new options --simplify-lines, --simplify-polygons, and --improve-overview - better handling of contour lines and lines in overview map (less zig-zagging/diverging of parallel lines) - direction flag is used with extended types (effects results of --allow-reverse-merge) - option --allow-reverse-merge is now also used for non-routable lines - better detection of obsolete points caused by rounding - different method to calculate and preserve "needed" points allows better line/polygon simplification http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4786

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low-res-opt branch ready to merge?
by Gerd Petermann 22 Jun '21

22 Jun '21

Hi all, I made no more progress to find a solution to detect parallel lines in the overview map. Too many special cases and almost no improvement with the simple cases. So, I think this should no longer block the merge to trunk. Mike suggested not to add new options --simplify-filter-line-errors / --simplify-filter-polygon-errors but instead enhance the syntax for the existing options --reduce-point-density and --reduce-point-density-polygon. I am open to that. What's better? Are there any other known problems with the branch? Any good ideas to improve something? Gerd

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Remove-obsolete on line with matching ends
by Ticker Berkin 17 Jun '21

17 Jun '21

Hi Gerd Here is a slight enhancement to low-res-opt RemoveObsolete. It is possible that this case (a b c c b a) will never happen because "c" will probably be de-duped. Ticker

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low-res-opt branch: error message from ShapeSplitter for self-intersecting multipolygon
by Gerd Petermann 15 Jun '21

15 Jun '21

Hi Ticker, please check https://files.mkgmap.org.uk/download/512/63240024.o5m with (unpatched) r4756 and these options --generate-sea=multipolygon,floodblocker --preserve-element-order --order-by-decreasing-area --allow-reverse-merge Produces an error message SCHWERWIEGEND (ShapeSplitter): e:\osm_out_work\norway\20210511_095323\63240024.o5m: Vertical split 36691968 failed on shape at http://www.openstreetmap.org/?mlat=65.979056&mlon=12.308790&zoom=17 Possibly a self-intersecting polygon for this invalid multipolygon : https://www.openstreetmap.org/relation/5294624 The result doesn't look wrong, so I think there should either be no error message or we need code to remove those self-intersections or ignore invalid MP like that? Gerd

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Documentation for the new Douglas-Peucker options in low-res-opt branch
by Gerd Petermann 15 Jun '21

15 Jun '21

Hi all, I've now added documentation for these new options, see: https://www.mkgmap.org.uk/websvn/diff.php?repname=mkgmap&path=%2Fbranches%2… Is it clear enough? I think the recommend value --reduce-point-density-polygon=8 is far too high at low resolutions. Should this be changed? Together with the new --improve-overview option this branch version can produce much better results for the lower resolutions. Gerd

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new option --improve-overview in low-res-opt branch
by Gerd Petermann 15 Jun '21

15 Jun '21

Hi all, the thread http://gis.19327.n8.nabble.com/Proof-of-concept-for-better-sea-in-overview-… got too confusing because posts with attached pictures where blocked for a while, and in the end it went private. Anyhow, I think the results are good now. For normal maps the performance doesn't change much, so I'd prefer to switch the option on by default but there is a problem with my "precomp sea test environment": http://gis.19327.n8.nabble.com/precomp-sea-test-environment-tp5974624.html which divides planet into just 34 tiles huge tiles. I'll see if I can improve that ... Gerd

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Proof of concept for better sea in overview map
by Gerd Petermann 12 Jun '21

12 Jun '21

Hi, the attached patch improves the overview map, but so far only when precomp-sea is NOT used. I tested it with --generate-sea=multipolygon,floodblocker so that mkgmap really has a multipolygon with the natual=sea data. For each level in the overview map it uses the original multipolygon data to compute the rings which will might visible at the given resolution. This requires more time compared to the current code but the result is much better and some fine tuning is possible. To be able to use this also with --precomp-sea we need some changes in the code which generates sea.zip so that one multipolygon relation for each tile is stored. I've uploaded the results here: https://files.mkgmap.org.uk/download/511/compare.7z What do you think? Gerd

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Commit r4767: raise minimum resolution of overview map to 13 to match the alignment of tiles produced by splitter with default resolution 13
by svn commit 11 Jun '21

11 Jun '21

Version mkgmap-r4767 was committed by gerd on Fri, 11 Jun 2021 raise minimum resolution of overview map to 13 to match the alignment of tiles produced by splitter with default resolution 13 This will slightly increase the size of the overview map but should also improve its quality near tile boundaries http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4767

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