[OSM-dev] Call to mobile developers: OSM binary file format

Milo van der Linden milovanderlinden at gmail.com
Thu Aug 7 11:22:40 BST 2008


Chris Browet wrote:
> 2008/8/7 Shaun McDonald <shaun at shaunmcdonald.me.uk>
> 
>> 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.
This is actually irrelevant for routing and I would even dare to say
that the integer format is a lot faster for routing. It would be better
to keep integers for routing and only transform the result to lat/lon
when it needs to be displayed.

As Stefan said: The format completely depends on the purpose it is
supposed to serve.


>>
>> http://trac.openstreetmap.org/browser/sites/rails_port/lib/geo_record.rb#L22
>>
> 
> Ok, so I guess this is one decision taken!
> 
> - Chris -
> 
> 
> 
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