Hi Colin,
I went through exactly the same process some time ago, and eventually
used a different source:
http://thematicmapping.org/downloads/world_borders.php
It would be nice to be able to extract something very similar from osm.
If you have any success, please share it.
Andy
On 30/08/10 10:05, Colin Smale wrote:
Hi,
I am trying to extract national boundaries from OSM and it's proving
more difficult than I anticipated.
What I would like to end up with, is a collection of complex polygons
(inner and outer rings including enclaves/exclaves), one for each
country. I thought I should be able to do that by getting all
relations with type=boundary, admin_level=2. Using XAPI I got a large
file which contains some of the information, but as some national
boundaries seem to be implemented using subrelations and
subsubrelations etc I now find I will have to query the database for
each subrelation individually and drill down successively until I have
all the ways I need. But that looks as if it will give me large
numbers of internal borders between lower-level admin units as well,
and it will be an enormous job to stitch everything together and
discard the internal borders.
For many countries there is a simple relation for the national
boundary, referencing a number of ways, which I can concatenate to
produce the complete outer boundary. But France and Slovakia for
example don't seem to have a single relation as a starting point.
I can't imagine I am the first person to want to do this. Has anyone
got any tips? Or maybe even a ready-made data set?
National boundaries don't change all that often, but it does happen
from time to time, so it would be nice if this could be repeatable in
the future.
Thanks in advance for any help you can give!
Regards,
Colin
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