[OSM-talk] Request for feedback: new building colours in openstreetmap-carto

Christoph Hormann chris_hormann at gmx.de
Tue Jan 6 18:20:01 UTC 2015

First i do not particularly like or dislike the new color, looking at 
this change only it seems to me in some areas and zoom levels the map 
appearance is improved, in others it is not.

But as i have mentioned on github i think in a broader consideration 
regarding the style as a whole this change goes in the wrong direction.  
Making the buildings much lighter further restricts the available color 
space for area colors (that is essentially all colors that could form a 
background to a building).  The available space between the background 
color of the map and the building color is extremely small to fit into 
that dozens of different area colorings and still be distinguishable.  
So far no suggestion has been made to address this i think.

We all know that the standard map style has a lot of technical 
constraints that make a good design difficult but you should not make 
the mistake to avoid hard decisions by creating ambiguities. The 
clarity of a map strongly depends on things that are shown to be 
clearly and distinctly shown and not too much stuff that is just 

Specifically this is a problem when showing buildings at zoom levels 
12-14 where the individual building often is hardly 1-2 pixels in size.  
In areas near the equator (where extensive building mapping is rare) 
showing buildings at z=12 is fully pointless and still doubtful for all 
but the largest buildings at z=14, see:


Even at very high latitudes at z=12 the smaller buildings are just 


And in areas with dense building coverage this is further aggravated by 
the way AGG renders polygons.

From z=15 on things look better, largely due to the outlining - low 
latitude cities still look crappy but more due to the roads than due to 
the buildings.

Part of why the brighter color might seem an improvement is that it 
creates less disturbing noise at these levels but this is just hiding 
the fact that displaying sub-pixel sized buildings does not make a lot 
of sense and it further smudges the already difficult to distinguish 
urban landuse colors.

In any case ultimately i think it is good to try things out this way - 
there is only so much you can evaluate in advance in a test deployment 
as it has been done for this change.  

Christoph Hormann

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