[OSM-talk] GPS point density map? (Was: Free the postcode maps)

[Nick Black]

Cheers Chris,

I'll take a look.

BTW, I think using OSM data to check/validate the FTP database would not
cause the FTP data to become subject to the OSM license, as the OSM license
does not explicitly mention checking/referencing, only re-use of the data.
 Which is good news for FTP.

On 7/5/06, Christopher Schmidt <crschmidt at crschmidt.net> wrote:
>
> On Wed, Jul 05, 2006 at 10:44:52AM +0100, Nick Black wrote:
> > On 7/4/06, Petter Reinholdtsen <pere at hungry.com> wrote:
> > >
> > >[Nick Black]
> > >> This isn't strictly OSM, but as FTP is a sister project I thought
> > >> I'd bug you guys anyway.  I've made a quick density map of the
> > >> current FTP database, which can be found here:
> > >
> > >What about making a density map of the GPX files uploaded into OSM?
> > >It would be fun to know where the most points are submitted. :)
> >
> >
> >
> > My guess - London.  I'll take a look.  I've been making these maps in
> > ArcGIS, but I'd like to start using GRASS a lot more.  Has anyone
> imported
> > the OSM XML into GRASS?
>
> Yep.
>
> > What would also be interesting would be to interpolate the points, set a
> > threshold, and see how the thresholded surface compares to the lines
> formed
> > by segments and ways.  Before I start doing this has anyone tried it
> before?
>
> Yep. Some documentation on the wiki:
>
> http://wiki.openstreetmap.org/index.php/Simplifying_OSM_Shapefiles
>
> $THRESH in this case is a threshold value for simplification.
>
> The 'minscales' where these threshold values were indistinguishable from
> the underlying map were:
>
> osm_semgent_0.01: 3,000,000
> osm_segment_0.005: 750,000
> osm_segment_0.001: 200,000
> osm_segment_0.005: 50,000
> osm_segment_0.0001: 20,000
>
> The approximate line counts moved in a mostly linear fashion from 20,000
> to 90,000.
>
> http://wiki.openstreetmap.org/index.php/Converting_OSM_to_GML should let
> you convert to GML, and from there to something like a shapefile, which
> I think you can then load into GRASS.
>
> (I did this all 4 months ago, so my memory may be hazy.)
>
> --
> Christopher Schmidt
> Web Developer
>
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