[GRASS-user] interpolating intensity points & r.in.xy

[M S]

Thanks for the great ideas.  Those sound promising.  I'll give them a whirl
and report the results!

Mark

On Mon, Jun 2, 2008 at 4:56 AM, Hamish <hamish_b at yahoo.com> wrote:

> Mark wrote:
> > I suspect the intensity data may be better for house extraction,
> > because the roofs are mostly all uniform in intensity clusters
> > values, where with RGB the roof shingles are far to varied for it
> > to classify them cleanly without other classes of non-roofs appearing
> > all over the map in scattered clusters.
>
> Hi,
>
> an idea about extracting roofs from LIDAR data- create a slope map from
> r.in.xyz DEM and run i.cluster etc. on that to extract areas of constant
> slope. Then threshold that to remove small area noise* (say under 25 sq-m)
> and large areas (roads, etc).
>
> [*] in vectors this would be 'v.clean tool=rmarea', not quite sure about
> cluster data, maybe r.grow/r.buffer the null cells then back the other
> direction and use that as a mask??
>
> Not sure how to separate "big box" Walmarts from parking lots, maybe if you
> set high slopes to NULL you can turn flat areas into islands, then test each
> island (r.to.vect areas?) for height departure from the surrounding DEM??
> perhaps something with r.neighbors?
>
>
> Hamish
>
>
>
>
>
>
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