Re: gnome-maps GNOME Maps offline trip planing

[Mattias Bengtsson <mattias jc bengtsson gmail com>]

CC'in the list as this discussion probably matters to the Maps project
as a whole.

On tis, 2013-07-09 at 17:44 +0200, Olaf Leidinger wrote:
> Maybe mapnik (http://wiki.openstreetmap.org/wiki/Mapnik) can be uses for
> that purpose. Although it doesn't use cairo but AGG. But personally, I
> think this is not bad, as AGG is much more optimized for software
> rendering than cairo.

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?
 - what dependencies does Mapnik have? 
 - 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.

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.

My guess is that making a new vector tile renderer in libchamplain is
the way to go on this either that or use (and update?) the libmemphis
one.

> I don't know much about the computing needs for offline routing,
> however, using OsmAnd, distances of 300 km and more are no problem for
> me. And that on an 1 GHz ARM device with 512 MB of RAM. So it seems as
> if their code is quite optimized.

We need to be able to show routes from a small street in Gothenburg to
an amusement park in Paris or Moscow too though. Doing these
calculations fast is hard and (I think) demands huge amounts of
precalculated cache. I'm in no way an expert on this though, but this is
my understanding from reading the OSRM (http://project-osrm.org/) wiki.

> > I didn't so thanks for your e-mail, do you know where the code is
> > hosted?
>
> Here are links:
>
>
> This is the Git repository for the core
>
> https://github.com/osmandapp/OsmAnd-core
>
>
> And this is a post on the mailing list concerning C++ port:
> https://groups.google.com/forum/#!msg/osmand/r6iMFwgn5g4/8sbFJ1cDGCwJ

Cool, thanks!

Regards,
Mattias