[Imports] [OSM-dev] Coastline changes Antarctica

Jochen Topf jochen at remote.org
Wed Mar 13 16:06:06 UTC 2013

On Tue, Mar 12, 2013 at 10:38:36AM +0000, Andy Allan wrote:
> On 12 March 2013 09:12, Tom Hughes <tom at compton.nu> wrote:
> >> I am not sure it is a good idea to switch to water polygons. Those
> >> polygons
> >> are much more complicated because they contain lots of holes, so they are
> >> slower to render. I'd only do that if really necessary (for instance when
> >> you want to mask something below the water polygon.
> >
> >
> > Interesting - that change was Andy's idea and I think the thought was to
> > reduce the damage done by any breakage and to ensure that we're not matching
> > any massive polygons in the busy (land) areas.
> So my line of thinking is as follows:
> 1) Jochen's proposed changes are going to break all coastcheck-created
> shapefiles, so openstreetmap-carto should instead use ones from
> OSMCoastline
> 2) Jochen does some form of QA for OSMCoastline so they are good to use directly
> 3) If you're not using hillshading, inverse vs normal makes no visual
> difference. But as soon as you use hillshading, you want inverse. So
> all else being equal, inverse should be the default
> 4) It's also confusing to have the map background as blue, when most
> people editing stylesheets think the background colour would be the
> land colour.
> 5) The vast majority of rendered tiles are all land. So it seems
> strange to draw a blue background, to immediately colour it with a
> land polygon, in almost every case.
> I take the point about the complexity of water polygons vs land
> polygons though, it's not something I'd thought of. I wonder if it
> invalidates the performance advantages described in 5) ?

In land areas in most cases you'll only have to draw one or a few very simple
rectangular polygons. I don't think this will take much time. Only coastal
areas will have more complex polygons, and they will have them regardless of
whether you have land or water polygons.

Maybe somebody should do a benchmark. :-)

Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298

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