[OSM-talk] Administrative boundaries export

Frederik Ramm frederik at remote.org
Thu Oct 3 10:41:21 UTC 2013


On 10/03/13 12:32, César Martínez Izquierdo wrote:
> Hi Frederik, regarding software, I am already familiar with Mapit
> scripts code, which are able to extract admin boundary polygons for each
> level (it is not creating relationships though). How do you see
> Nominatim or Osmium/osmjs better for the purpose? Reading osmjs
> documentation, I see it could be used to build a similar script to mapit
> one (which uses a local instance of OSM3S api). Do you think it would be
> faster?

I would think so. The Mapit stack is very convoluted - as far as I
remember, it first extracts stuff from a planet file with Osmosis, then
imports that into osm3s (aka overpass), then makes queries from there.
This is a very complicated way to do it - with an osmjs/osmium based
program you'd process the planet once and that's it (if using OGR output
like in the osmium_toogr example you can even generate KML directly),
and the time spend would very likely be much less than even the initial
Osmosis step of the Mapit stack. I'd assume it would take a couple hours
for a full export.

Of course if you're already familiar with the Mapit stack and it works
for you, that's fine too.

> - using one of these tools to do a first export, which should be later
> processed by a separate script in order to make sense on the
> particularities of each country.

Yes, I think that makes sense, however keep in mind that depending on
how you do the export, some things might already be broken at that
stage, and no chance for a program down the line to fix it. The export
process would probably have to be modified to export a collection of
broken things in addition to the working things, so that a script down
the line can then do something with the broken things.


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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