Google Summer of Code 2016 - improving openstreetmap-carto

Posted by Mateusz Konieczny on 14 June 2016 in English (English)

During GSoC 2015 I focused on improving road presentation in the Default OSM map style. This year I am again participating, but with more diverse goals. I am planning to improve performance, reduce rendering order problems and tune mid-zoom level rendering.

mid-zoom level rendering

I started with work on improvements to mid zoomlevels (z6 to z9). During search for the best and most promising ways to improve rendering, starting from trawling through reported issues. I also prepared and submitted some additional tweaks like rendering names for barriers, fixing viewpoints and forests and shops and other.

I am also like during GSoC 2015 preparing a comparison between the current map style and alternatives.

A bit of history

There are some visualisations showing how data was added to OSM. But I have neither seen nor found something similar for a map style. So, for start of next big series to the map I made a display of what was changed in the past.

Visualisation are available for z18 z18

z14 z14

z8 z8.

I selected Weybridge as location as map of this place was the first OpenStreetMap-based map to go on Wikipedia.


As usually testing and review is welcomed for open pull requests, especially one considering rendering names for barriers and an associated popular tagging mistake.

I am considering to look more for inspiration/comparison in printed maps. I looked for online sources and for now I found surprisingly small number of contemporary maps that would display sort-of-similar set of symbols as Default OSM style, with scale within z5 - z10 range.

From promising findings I caught David Rumsey Map Collection and Wikimedia Commons (enabling CCI allowed to find something).

But I found nothing highly useful. For now

are the best. Is anybody aware about maps or database of maps allowing to find maps similar in content to Default OSM Style, with scale within z5 - z10 range?


Thanks to Paul Norman for simplified osm2pgsql database dump. Without that resource obtaining database for lower zoom levels would be far more complicated.

Location: Kosocice, Swoszowice, Krakow, Lesser Poland Voivodeship, Poland

Comment from imagico on 14 June 2016 at 20:06

As you know z5-10 is fairly hard to significantly improve without preprocessing data.

Regarding print maps for comparison - you can find a lot of historic maps on

Good contemporary general purpose maps at these scales are quite rare - some atlases might provide fairly good examples although there is not much progress in technical aspects and overall quality in the last 20 years or so in those.

The range of scales we are talking about here is from about 1:20M (z5 at the equator) to about 1:200k (z10 at about 70 degrees) - towards the latter you will also find a lot of examples among national mapping services.

But keep in mind that not everything that works well in print is equally suited for a digital map.

Comment from nebulon42 on 14 June 2016 at 20:25

Interesting idea, coincidentally I was preparing similar visualizations for a talk at FOSSGIS. I did not prepare a low zoom one, so it is good to have an additional (linkable) resource. :)

Comment from alexkemp on 14 June 2016 at 21:48

I’m not sure of the actual z-level used, but the following link is a pdf that includes a current map derived from UK Ordinance Survey data:

Gedling Council Street Guide

Coincidentally, this link is included within my latest diary entry (posted the one before you!).

Comment from Sunfishtommy on 16 June 2016 at 02:24

I just wrote a diary post about rendering issues with national parks. Basically along oceans national parks cover up coastline with large green blobs. But they do not do this with lakes. I a starting to deduce that it might have to do with the leisure=park key. It needs to be fixed though, because currently a lot of detail is being covered by these big green blobs.

Is this something we can fix? It seems like it might be as easy as making leisure=park render under ocean.

Link to my diary entry about the problem.

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