[maemo-developers] Maemo-mapper vector data backend follow-up

Tue Sep 23 22:09:12 EEST 2008

Hi,

do you want an honest reply: Don't do that. Maemo-Mapper isn't meant to handle
vector data. Period.

These are my concerns:

- Plenty of duplicate data will get stored that isn't required since Maemo-Mapper 
  will locally cache tiles that have been generated on the device itself.

- Rendering is less than optimal because Maemo-Mapper asks for tiles. You'd 
  have to a) render most things several times as most objects will span several 
  tiles and b) have to render more data than required as Maemo-Mapper does
  some caching in advance.

- You'd need massive interfaces between your renderer and Maemo-Mapper for
  all kinds of interaction with the maps. You'd e.g. have to communicate
  POI details, street details, etc etc ...

- The entire thing will not be trivial to use and debug as you are basically
  planning to cut an already complex navi application into two parts which
  then need proper coupling.

- All navigation functionality of Maemo-Mapper is imho done on an external
  server in advance. You'd also have to port a navigation engine onto maemo
  and couple it with maemo-mapper as well as with your tile renderer.

I'd rather use software that was designed to use vector data. E.g. navit has
been ported to maemo by a bunch of people incl. myself. We all didn't put
much effort into this and the results are barely useable. But it's imho way
more effective with respect to vector data to continue with a program like 
navit than Maemo-Mapper.

Regards,
  Till

Am Dienstag 23 September 2008 schrieb Simon Pickering:
> Hi all,
> 
> A few of us sat down with John Costigan (aka Gnuite) after his presentation
> at the Maemo Summit and as well as drinking a few beers/vodkas discussed how
> to achieve the end goal. I just thought I'd start the conversation going
> here and summarise my thoughts (John has probably not even made it home
> yet!).
> 
> For those who didn't see the presentation, it was basically asking for input
> on how to use vector data as a backend to provide tiles and routing
> information, without needing to completely re-write Maemo-mapper and change
> the way it handles data.
> 
> The idea that John presented was that we should store the vector data
> locally and act like the OSM/Google server and serve Maemo-mapper with image
> tiles and route GPX data in just the same way as already happens. The
> advantage here is that the two projects are pretty well separated (though
> John said he'd be happy to make alterations to Maemo-mapper if needs be).
> 
> The other positive aspect of this split is that if someone were to reverse
> engineer the TeleAtlas/Navteq storage format, which might be slightly
> controversial, it wouldn't impact on Maemo-mapper or any other backend (e.g.
> OSM).
> 
> So, considering OpenStreetMap as our vector data set (Garmin is another
> option as I believe there's an open source library which can understand
> their database format; likewise for British University users Ordnance Survey
> data is available; and for those in the US there is Tiger census data;
> world-wide NASA Shuttle Radar Topography Mission contour data; i.e. there's
> at least a few sets of data which could be used), these are my initial
> thoughts.
> 
> The OSM data is stored in a MySQL data base (though the data we download as
> *.osm is an XML dump I think); there is an API to query the database using
> XML. As we'd already be running as a server, and would gain no advantage in
> using the API should the database format change (as we access the database
> directly, so need to implement the db-side of the API), I would propose we
> ignore that, and act on the data directly, should we decide that it doesn't
> need pre-processing. The only disadvantage to this, it that if we
> implemented the API, we could also work online and talk to the main OSM
> database directly. Not sure how much use/interest there would be in that.
> Thoughts?
> 
> So, we have some data, now we have to be able to do something with it. There
> are a number of programs which can render OSM data that we should look at
> adapting rather than writing it all from scratch. 
> 
> Tile rendering
> ==============
> 
> There's a list of OSM rendering programs here [0].
> 
> Mapnik [1] is the program which renders the map tiles currently downloaded
> by Maemo-mapper. This requires that the OSM MySQL database be processed and
> turned into a PostGIS database. It doesn't look like this is something that
> could be done on-device due to the time and memory requirements. PostGIS
> rendering is probably a good thing as other map data is stored in this
> format. This is supposed to be difficult to setup though, and I don't know
> the cpu/memory requirements.
> 
> Other applications such as Navit [2], Gosmore [3] also require that the
> database be processed to turn it into something other than MySQL. Pyrender
> [4] might be a possibility, though it is designed to work from a tile server
> (where a tile is a tile of metadata rather than image data) rather than the
> MySQL database.
> 
> I'm tempted to quickly pull together something using pyrender (it currently
> parses XML directly afaik, so will need some tweaking to read from MySQL if
> that's the backend of choice). Using a proper db rather than parsing the XML
> should hopefully allow it to scale better than it is supposed to do atm.
> 
> Obviously C will be faster, but perhaps more people will get involved if
> it's Python...? Any thoughts on this?
> 
> 
> Navigation/routing
> ==================
> 
> Again, there are a number of programs which do this [5]. Again Gosmore [3]
> and Navit [2] and another Python program, Pyroute [6], are on the list. I
> don't know much about these, how processor intensive they are or how fast
> they are. Does anyone have any ideas?
> 
> Pyroute appears to use raw OSM vector data (though not as a MySQL database
> as that's not a dep, unless that's assumed for a Python install?); Navit and
> Gosmore both use their own converted data formats.
> 
> Again I'm tempted to try using Pyroute with a MySQL db. Same arguments as
> above.
> 
> 
> So to summarise, it looks to be possible. Let discussion commence!
> 
> Cheers,
> 
> 
> Simon
> 
> 
> [0] http://wiki.openstreetmap.org/index.php/Rendering
> [1] http://wiki.openstreetmap.org/index.php/Mapnik
> [2] http://wiki.navit-project.org/index.php/OpenStreetMaps
> [3] http://wiki.openstreetmap.org/index.php/Gosmore
> [4] http://wiki.openstreetmap.org/index.php/Pyrender
> [5] http://wiki.openstreetmap.org/index.php/Routing
> [6] http://wiki.openstreetmap.org/index.php/Pyroute
> 
> P.S. Rana is a combination of Pyroute and Pyrender, search for it on the osm
> wiki.
> 
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