[Talk-us] Whole-US Garmin Map Update

[Greg Troxel]

Dave Hansen <dave at sr71.net> writes:

> On Wed, 2009-11-18 at 18:50 -0500, Greg Troxel wrote:
>> Dave Hansen <dave at sr71.net> writes:
>> 
>>   roads are disconnected at state boundaries due to being cut with a
>>   non-splitter tool.  (splitter has special logic to insert nodes on
>>   ways at tile boundaries.)  I think I had this problem when using
>>   e.g. massachusetts.osm.bz2 and vermont.osm.bz2 together into splitter
>>   - driving from central mass to vermont had routes reverting to basemap
>>   but when I crosssed into VT they became sensible.
>> 
>>   When making maps of a state, splitter makes tiles that fit the x/y
>>   bbox, and these will in general go beyond the state border.  When you
>>   do this with neighboring states, typically you'll get overlapping
>>   tiles that will have data in the state and no data out of state,
>>   mirror image.  It's not clear what the draw order is for areas covered
>>   by both tiles, but any particular order can't be right.
>
> Yeah, that's true.  But, take a look at the new set from Lambertus.  He
> does it with non-overlapping (generally) bounding boxes.  I'm not sure
> the second set I posted have this issue.

I had managed to forget all about what Lambertus has done.  His maps are
based on running splitter on the planet.  So the .img tile areas are a
proper division of the world, with no overlaps.  You can't necessarily
get exactly a state, but that's perfectly ok.


>> To make a gmapsupp.img for all of the US, I was going to get a US
>> extract of the planet, use splitter, and then use mkgmap with routing
>> enabled.  I would then use gmapibuilder to put into RoadTrip so I can
>> load the parts I want together with the proprietary map (for when I
>> actually have to get somewhere :-(). That should address all three
>> issues above.
>
> Cool!  Please do share when you get this done, it would be awesome.

I think the only thing missing in what I do now is to have a US extract,
and maybe enough RAM.  I've been working on getting good results from
mkgmap and asking lots of questions on the mkgmap-dev list.

I have attached the script I use to build maps, do-mkgmap.  I call it
as:

$ do-mkgmap massachusetts.osm.bz2 vermont.osm.bz2 [....]

This method the routing-broken-at-state-borders problem, but not the
overlapping tiles problem.  It should work with a united_states.osm.bz2;
apparently that's a high enough fraction of the size of the planet that
it isn't produced.

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