[OSM-talk] High Cartographic Quality Label Placement on OSM-based Map

[Maxim Rylov]

7/12/2013 12:18 AM, Christoph Hormann wrote:
> Could you explain in what ways this is the case. Since different types 
> of labels are shown in various maps direct comparison is difficult. 
> You seem to very well avoid overlaps between labels and none the less 
> you are able to put quite a lot of them on the map but non-label 
> feature do not appear to play a role in label placement and there are 
> some strange priorities. Is the algorithm available as open source? 
> Greetings, 

Avoiding of overlaps in map labeling is a constraint that is necessary. 
We can compare the map labeling on osm.org and on our map with the help 
of the list of cartographic rules for point-feature labeling.

For example, they are:

*  R1. *Type arrangement should reflect the classification, importance 
and hierarchy of objects.

*R2.*The lettering to the right and slightly above the symbol is 
prioritized.

*R3.*Names of coastal settlements should be written in water.

*R4.*Label should be placed completely on the land or completely on the 
water surface.

*R5. *Names should not be too close to each other

*R6.*Labels should not be excessively clustered nor evenly spread out.

*R7. *Each label should be easily identified with its point-feature. 
Ambiguous relationships between symbols and their names must be avoided.

*R8. *Label should not overlap other significant features of the 
cartographic background or do it as little as possible.

As far as I know Mapnik and other open-source software take into account 
only the rules R1, R2 and R5 (partially, returns labels that are evenly 
spread out, example - http://maps.skobbler.com/on z11).
And the "greedy" algorithm that is utilized to solve the label placement 
problem returns rather poor approximation to the optimum as there is no 
backtracking.

> Is the algorithm available as open source?
Unfortunately, the algorithm currently is not open-source, but the model 
that we elaborated and used will be published as a journal paper within 
the next few months.



All the best,
Maxim Rylov
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