[OSM-talk] The long tail - lowest common denominator

[Christopher Schmidt]

On Mon, Jul 10, 2006 at 09:17:29AM +0100, Nick Black wrote:
> On 7/9/06, Lars Aronsson <lars at aronsson.se> wrote:
> >Nick Black wrote:
> >
> >> I'm not sure that I am  following you Lars - do you mean that we could
> >> use automatic feature detection to detect the edges of water features?
> >
> >Yes, that's what I was philosophizing about.  But I haven't tried
> >it or even planned to try it.  I'm far too lazy for that.
> 
> One of the most significant features of the SRTM as a global dataset
> is that it is self-consistent and internal errors fall within
> specified and documneted thresholds.  This was acheived by a lot of
> post-processing work.  Part of the work involved created a global
> water bodies mask at the same scale (1 arc-second/3 arc-sec) as the
> complete topographic dataset.
> 
> The mask is called the SWBD.  It is supplied in ESRI shapefile format
> and is downloadable from the same ftp site as the SRTM data:
> 
> ftp://e0srp01u.ecs.nasa.gov/srtm/version2/
> 
> So thats cool - Free 3-arc-sec water body data.  Well, its only as
> cool as the one degree tiles that it is supplied in.  If someone could
> process this data to derive a complete water-bodies mask it would be
> invaluable to OSM and to other projects.  A derived version of the UK
> SWBD is already up on Chris's OSM freemap site, where is really shows
> up the VMAP data (shows how coarse it is).

Oh, you didn't mention this data was so easily available -- I don't know
about processing it into a single shapefile (which seems like it should
be almost trivial), but I can absolutely set it up so that it's rendered
-- should this be in addition to the water layer you offered me, or
should I just drop that one and use the worldwide data instead?

-- 
Christopher Schmidt
Web Developer