Re: gnome-maps GNOME Maps offline trip planing

[Olaf Leidinger <oleid mescharet de>]

Hej!

> Yeah, and as you say in your other email Mapnik can render via Cairo
> too. This might be something to look into later. If you want to do some
> research on this it would be really helpful. What we would need to know
> is:

>  - are there any good vector tile format that mapnik also 
>    can read? I think Mapbox has been working on this
>  - Are there any good map servers that can serve these vector
>    tiles?

Maybe this one is of interst:
http://openstreetmap.us/~migurski/vector-datasource/

Also, this is a list of all the plugins mapnik supports:
https://github.com/mapnik/mapnik/wiki/PluginArchitecture

However, I can't judge which are the right sources to use. 

>  - what dependencies does Mapnik have? 

This is an extract of the lastest mapnik ebuild. I removed default
stuff on which gnome depends anyway. The ones with the question mark
are optional.

        >=dev-libs/boost-1.48
        net-misc/curl
        sci-libs/proj
        x11-libs/agg
        dev-cpp/cairomm
        dev-python/pycairo 
        gdal? ( sci-libs/gdal )
        geos? ( sci-libs/geos )
        postgres? ( >=dev-db/postgresql-base-8.3 )
        sqlite? ( dev-db/sqlite:3 )

>  - is it reasonable to run it on a desktop computer? We used to
>    run Mapnik with TileStache on our servers at my old work but 
>    I have no idea how it fares on a desktop computer.
>  - How fast is the rendering? It needs to be comparable to using
>    online maps in libchamplain.

I can only tell about the OsmAnd renderer. On my mobile, it is getting
slow as soon as I enabled every detail including height maps and such.

The source code repository of OsmAnd also includes a C++ port of their
renderer, however, it is Qt based.
 
> The reason for me talking about vector tiles is that we can't reasonably
> expect the user to download map data before using Maps. The app should
> just work when started. The benefits of using vector data is obvious
> when you need to work offline though which makes vector tiles a good
> middle ground.

So obviously, vector rendering should be an option, but
downloading the tiles from the web (including a local cache) should be
default.

I have the feeling that it all comes down to either:
 1. Provide pre-processed OSM data as download, as OsmAnd does or
 2. find a free vector tile server or
 3. implement the download from OSM and perform the conversion to a
    usable format locally. 

Number three is probably quite slow. I remember aborting the
import of Germany to a Postgre-SQL database after several hours.
Probably number one is the way to go.

Best,
Olaf