[mkgmap-dev] Splitting at country borders?

Sun Sep 20 22:44:36 BST 2009

Marco,

There is a problem with Geofabrik downloads and it is not possible to  
combine 2 of them into a complete osm file.
  Since they provide it for free we can't complain. Instead we have to  
use other methods. I am sure Geofabrik does that for a reason because  
there are other use cases than Garmin routing.
For a user it should matter if tiles are across borders. they will  
need all tiles from denmark to italy. why not simply create whole  
europe and a user downloads the tiles needed.
Lambertus offers exactly such a service already at http://garmin.na1400.info/routable.php 
  why would anyone split the map into more tiles just to stop at the  
border?
since inter tile routing is still not perfect try to keep tiles as big  
as possible.

On 20 Sep 2009, at 11:50 , dom Team OiD wrote:

> Apollinaris,
>
> I don't know if you questions was directed to my,
> but to create a map which alows routing drom kopenhagen to rome, I  
> have
> to take a full europe map.
> It is not possible to download demark, germany, austria and italy,
> because routing is not possilbe then.
> routing only works if I take europe and create a map out of this.
> I'm providing these maps fordownoad. In this case the user can  
> download
> a denmark, ermany, austria and italy map and
> is able to route over map/country borders. Currently the user must
> always download the whole europe map.
>
> Marco
>
> Apollinaris Schoell schrieb:
>> On 19 Sep 2009, at 4:29 , Johann Gail wrote:
>>
>>
>>>> So is it possible to configure the splitter do split the maps not
>>>> after
>>>> x-Number of nodes but at these coordinates?
>>>>
>>>>
>>> No, this is not what I have written. There is some  
>>> missunderstanding.
>>> The recent splitter is not able to split at geographical boundaries.
>>> This is the task of osmosis.
>>>
>>
>> even osmosis can't do that. osmosis takes a polygon as input and
>> doesn't read boundaries from osm files
>>
>>
>>
>>> Maybe it is not too complicated to build this feature into splitter,
>>> but
>>> at the moment it doesn't.
>>>
>>
>> neither splitter or osmosis insert new points. but it is required to
>> have boundary nodes in mkgmap. splitter would need to calculate
>> crossing points with the boundary or a provided split polygon with  
>> all
>> ways and insert the boundary points.
>>
>>
>>>> Or is it posilbe to do a presplit, which creates a tile for each
>>>> country
>>>> and then in a second step splitting the country files?
>>>>
>>>>
>>> Yes, this way should work. But for the presplitting you can't use
>>> splitter. I don't use osmosis by myself, so I don't know internals  
>>> of
>>> it. But I know, that geofabrik splits its regions with osmosis.
>>>
>>
>> you can do the presplit but routing can't work then across  
>> boundaries.
>> osmosis has different modes
>> - clip ways at the boundary -> no routing across tiles due to missing
>> nodes
>> - include the whole way ->  long ways extend far beyond the boundary,
>> areas aoutside the boundary will be incomplete, tiles will overlap in
>> huge areas. routing may break in these overlap tiles
>> - don't clip the way but omit the points outside the box/polygon ->
>> combining 2 osm files should work. but then why did you split them?
>>
>>
>>
>>
>>>> Then it would be possilbe to download europe from geofabrik,  
>>>> split it
>>>> into countries and then crate maps from it.
>>>> These maps would be interroutable. It would be also need less
>>>> computing
>>>> power/memory for doing this compared of
>>>> processing the whole europe map
>>>>
>>> I would expect the interstate routing to work. Precondition is
>>> obviously
>>> that the presplitted tiles don't miss any segments at the border and
>>> the
>>> border nodes have exactly the same coordinates.
>>>
>>>
>>
>> still don't understand why this is useful. If you want multiple
>> countries and route across countries and tiles why split it more than
>> necessary and try to assemble again?
>>
>>
>>> Regards,
>>> Johann
>>> _______________________________________________
>>> mkgmap-dev mailing list
>>> mkgmap-dev at lists.mkgmap.org.uk
>>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>>>
>>
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>>
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