I currently use my own implementation for my java mobile routing and navigation
implementation (see we-travel.co.cc), though I would be very happy to switch to
a common implementation or help develop such an implementation if this fits my
needs.
Some rough high level requirements:
- data needs to be very compact, but also quickly fetchable
- data needs to be devided in manageable, self contained chunks. Some marginal
data duplication is needed to keep the correct references.
- an index system is needed to quickly find any element in the data (currently
about half my total data size are indexes!)
- floats are a no-no (many mobile phones don't even know what they are or are
extremely poor at handling them)
- Data must be ordered,sorted and indexed to allow quick retrieval for display,
lookup but also routing purposes. Some trade off need to be made here
- To make data is compact as possible, I currently store the coordinates
relative to some kind of tile structure. As such, I only need 3 bytes/point.
- Node-id's would be nice to have, but are really too much of data if you want
to store a full country like Germany on a mobile phone
- Most importantly (but most complicated as well) : in countries like the
Netherlands, each route section between 2 crossings has his own way id. This is
just too much for any routing engine on a mobile phone. I create a new way
index based on uniquely interconnected pieces of road with a common set of
attributes. I would very much appreciated if this type of logic could be
applied on the actual osm data. Anybody else has the same problem ?
- Common tags need to be structured in some compact binary encoding (waytypes,
roundabouts, oneway, ...)
- Must be utf8 compliant
Great initiative, hope this is going somewhere !
> Date: Thu, 7 Aug 2008 10:47:55 +0100
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]
> CC: dev@openstreetmap.org
> Subject: Re: [OSM-dev] Call to mobile developers: OSM binary file format
>
> Chris Browet wrote:
> >
> >
> > Do you think about floating-point or fixed-point
> > coordinates?
> >
> >
> > This is one of the things to discuss. For mobile applications,
> > fixed-point is the most efficient but we have to balance this with the
> > loss of precision.
> Actually the OSM db stores the node's lat and lon as integers. There is
> a scaling factor of 10000000 done on the fly when you read and write notes.
> http://trac.openstreetmap.org/browser/sites/rails_port/lib/geo_record.rb#L22
>
> Shaun
>
>
> _______________________________________________
> dev mailing list
> dev@openstreetmap.org
> http://lists.openstreetmap.org/listinfo/dev
_________________________________________________________________
Ontdek de snelste manier van communiceren!
http://www.startmessenger.be/nl/index.asp
_______________________________________________
dev mailing list
dev@openstreetmap.org
http://lists.openstreetmap.org/listinfo/dev
