[Routing] Binary file format

[Adrian Stabiszewski]

Hi Adam,

I didn't know your page on that topic. To be honest, I haven't searched the
wiki for this kind of information but I'm more and more surprised how much
info there already is ;)

I thing that this is basically the same idea, but my approach is to have all
data offline on a flash card with me. 

I will look into your concepts and see what we could use.

Regards,
Adrian.


> -----Ursprüngliche Nachricht-----
> Von: routing-bounces at openstreetmap.org [mailto:routing-
> bounces at openstreetmap.org] Im Auftrag von Adam Boardman
> Gesendet: Montag, 10. Dezember 2007 22:10
> An: routing at openstreetmap.org
> Betreff: Re: [Routing] Binary file format
> 
> Adrian,
> 
> I've been working on:
> http://wiki.openstreetmap.org/index.php/OSM_Mobile_Binary_Protocol
> 
> Which is basically a vector tile base mechanism for downloading OSM
> data.
> 
> With a view towards routing over the data (and trying to keep the data
> as small as possible) I've been planning to parse the data on
> downloading the tile in the mobile device and match up nodes that appear
> in more than one way and mark them as junction nodes, along with
> distances to other junction nodes. All that data would then be saved in
> the db, I'm not convinced that the processing power of mobile phones (my
> target device) is such that this is not possible with the latency of
> network connections and flash file system save speeds would make it
> worth doing server side.
> 
> Having said that the binary protocol is designed to permit differnet
> clients request different reply data so some clients could request
> server generated routing tables, and others not.
> 
> My next planned improvement to the PHPProxy code is to support relations
> (currently ignored), but to make them useful by automatically creating
> extra ones server side (in the proxy so would use negative id's, only
> valid for that tile) if it would reduce the data to be transmitted. So
> two (or more) consecutive ways that have the same name (or other key
> assignments), remove the key values from the way, and ceate a relation
> that references all ways and has one copy of the name/key values.
> 
> If were talking two ways that have the value ref=A7, then I'd making a
> whole relation (4+1+1+2+4+4) = 16 bytes is more costly than storing the
> data directly in the way (1+2+1+2) = 6 bytes, so in that case we wouldnt
> do it, but in the case of two ways of Princes Street (4+1+1+14) = 20
> bytes extra for relation, or in way (1+14+1+14) = 30 bytes, then you
> would.
> 
> The best thing would of course be to have these kind of relations
> automatically created by the API in the main OSM database, they would
> then have official ids and I wouldnt have to worry about assigning
> local ID's on the client for any negative ones. Also relations would
> then work crossing tile boundarys much better.
> 
> Cheers,
> 
> Adam.
> 
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