[mkgmap-dev] Option to output polygons in size order

Sat Jul 23 21:00:12 BST 2016

Hi Gerd

I don't understand how multi-polygon processing works, but was
presuming that, if my idea works, sorting on the size of each
individual polygon is the correct thing to do.

Partial overlap of polygons is generally not a problem I'm trying to
solve here, and it is unlikely that, say, if there is a field next to a
wood with a lake spanning the two, the mapping data would have 2 land
areas fully abutted with the lake overlapping both; I'd expect there to
be 3 distinct, non-overlapping, areas.

Ticker

On Sat, 2016-07-23 at 19:23 +0000, Gerd Petermann wrote:
> Hi Ticker,
> 
> mkgmap analyses multipolygon relations and cuts inner parts, so
> correct mp-relations
> should not be a problem. I've seen overlapping polygons, e.g. when
> you chose to render
> place=island and also the land polygons created by the sea generator.
> You suggest to write the larger polygon first, but in those cases
> this would not help.
> I think this solution would also not help when polygons partially
> overlap.
> 
> Gerd
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> Gesendet: Samstag, 23. Juli 2016 20:42:02
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] Option to output polygons in size order
>  
> Hi
> 
> I'm sure that the order in the map has some effect on the Legend; as
> I
> zoom in or scroll across areas with greenery they appear briefly and
> are then cleared, by the island polygon that covers everything, as it
> starts drawing the ways...
> 
> Generally, the openStreetMap data order is OK, but I have found
> examples where there are lakes, within the same meadow, that occur
> both
> before and after it. Not sure if this is related to multi-polygons,
> but
> if sorting was performed on the individual polygons there wouldn't be
> any problem.
>  
> Also it looks like splitter is delaying the British Isles (and other
> large) polygons because they occurs on multiple tiles.
> 
> Typ _drawOrder cannot solve the problem when there are nested
> polygons
> with more that one instance of the same type, whereas drawing outer
> ones first solves it completely.
> 
> I have seen mention somewhere that areas with the same _draworder are
> rendered in file order
> 
> Ticker
> 
> On Sat, 2016-07-23 at 17:17 +0000, Gary Bamford wrote:
> > Hi Ticker/Gerd
> > 
> > The draw order does work for the Legend ( it is the device I have
> ).
> > I also came across problems with multiple polygons, the problem can
> > be one of several things, not all multi polygons are correct on
> > openstreetmap, I cam across one today "fairhaven lake"  golf
> course,
> > was hiding, due to draw order, but the problem was, it is contained
> > within a polygon for a residential area, so I had to change the
> data
> > on openstreetmap, to make it an inner polygon. when i download the
> > new OSM data I expect it to work correctly.
> > 
> > if the polygons are set correctly on openstreetmap, then draw order
> > will will as you expect. 
> > 
> > Gary
> > 
> > From: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> on behalf
> > of Gerd Petermann <GPetermann_muenchen at hotmail.com>
> > Sent: 23 July 2016 17:05
> > To: Development list for mkgmap
> > Subject: Re: [mkgmap-dev] Option to output polygons in size order
> >  
> > Hi Ticker,
> > 
> > are you sure that the order matters? I've never heard that theory
> > and I would be surprised when that is true.
> > The normal way to handle the draw order is to use a typ file, not
> > sure
> > if this works on your device, but it seems to work well for others.
> > 
> > Gerd
> > Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> > von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> > Gesendet: Samstag, 23. Juli 2016 18:45:59
> > An: mkgmap development
> > Betreff: [mkgmap-dev] Option to output polygons in size order
> >  
> > Hi
> > 
> > I'm using splitter-r437/mkgmap-r3676 to make a map for Etrex Legend
> > from british-isles-latest.osm.pbf from geofabric.de.
> > 
> > Using "default" style and not using a TYP file, no land features
> > (woods,marsh,green) show because an island polygon for "British
> > Isles"
> > is rendered near the end, on top of everything else. I guess that
> the
> > Etrex has all area types as the same draworder and renders them in
> > file
> > order.
> > 
> > I presume I could use TYP / _DrawOrder to change this behaviour
> > slightly but I keep finding examples of woods in islands in lakes
> in
> > marsh in islands etc etc, so _DrawOrder can't solve the problem.
> > 
> > What would make everything show correctly would be to output
> polygons
> > in size order, largest to smallest. Could this be done easily?
> either
> > in splitter then --preserve-element-order, or in mkgmap, possibly
> > after
> > style processing because there will be a lot fewer polygons at this
> > point.
> > 
> > Regards
> > Ticker Berkin
> > 
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