[Talk-it] Fwd: Differences between osm.org tiles and WMF tiles

Federico Leva (Nemo) nemowiki a gmail.com
Mar 7 Feb 2017 06:56:40 UTC


Un sunto piuttosto utile su alcuni ulteriori motivi per cui serve 
https://maps.wikimedia.org/ .

Nemo

-------- Messaggio inoltrato --------
Oggetto: 	Re: [discovery] Differences between osm.org tiles and WMF tiles
Data: 	Mon, 06 Feb 2017 19:19:18 -0800
Mittente: 	Paul Norman
Rispondi-a: 	A public mailing list about Wikimedia Search and Discovery 
projects <discovery a lists.wikimedia.org>
A: 	discovery a lists.wikimedia.org



On 2/6/2017 1:16 PM, Erika Bjune wrote:
> Hi Svetlana,
>
> While we do get data from OSM, we run our own tile server called
> Kartotherian <https://github.com/kartotherian/kartotherian>, mainly
> for the following reasons:
>
>   * OSM's infrastructure is fragile and has cache challenges
>   * Their datacenter is in London, which means latency becomes an issue
>   * OSM's rendering stack can't scale horizontally well enough to be
>     sure they could handle our load
>   * Their map style is not mobile friendly
>   * We require multilingual and vector tiles, which their stack can't
>     do (currently)
>   * We wanted to provide nicer map styling in general
>

As a developer of both the WMF styles, OpenStreetMap Carto, and many map 
rendering components, I can provide some more detail. I'm not a server 
admin for either WMF or the OSMF, but I work closely with them.

The default "standard" map on OpenStreetMap.org is a style called 
OpenStreetMap Carto (osm-carto). The particular tiles being served on 
osm.org (tile.osm.org) are rendered on OpenStreetMap Foundation (OSMF) 
resources. Their usage is controlled by the tile usage policy 
<https://operations.osmfoundation.org/policies/tiles/>, which would 
prohibit their use as a default map on Wikipedia.

Aside from the policy reasons, tile.osm.org is not designed for 
Wikimedia's use, mainly because tile.osm.org is designed for providing 
mapper feedback, not efficient rendering.

- tile.osm.org is designed to show changes in OSM data minutes after 
they were made. The cost of this is that caching is much less efficient, 
and more resources have to be used for each map view. Wikimedia doesn't 
need minutely updates, and I think right now updates daily. Most 
commercial OSM hosts also update hourly, daily, or weekly. This decision 
shows up throughout how tile.osm.org is setup, sometimes in subtle ways

- tile.osm.org is not designed for multiple similar styles, e.g. high 
resolution "retina" tiles.

- tile.osm.org isn't designed to export static map images, which is an 
important WMF use case

- The tile.osm.org rendering stack doesn't provide some WMF-specific 
functionality needed, like integrations with Wikidata, etc.

- Parts of the tile.osm.org rendering stack are in maintenance mode and 
have no active developers. This is fine if they do what you need, but 
would have been a problem for WMF needs

For the record, I do think a deployment for WMF using the same software 
as tile.osm.org would have been possible and met the load requirements, 
but not have worked with static maps, multilingual maps, and some other 
WMF requirements

I feel OpenStreetMap Carto, the style on tile.osm.org, is a good style 
when you look at its goals 
<https://github.com/gravitystorm/openstreetmap-carto/blob/master/CARTOGRAPHY.md#main-goals>. 
Two of the goals are showing the richness of OSM data and providing 
mapper feedback. It doesn't have the goal of being a map where you can 
layer additional data on top, which is a key WMF use-case. Two osm-carto 
policy decisions that would have been a problem for WMF use are the use 
of only OSM data whenever possible, and rendering everything in the 
language of the region. The first is a problem because it requires 
design decisions which sacrifice cartographic quality, performance, and 
complexity, particularly at low zooms.



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