[GRASS-user] Road Extraction from HRI

[tommaso]

Hi all,

I'm trying to extract a urban road network from Quickbird imagery. 
The first question is: did someone already something similar? is it
really possible?

Now the technical questions: I have the RGB and NIR with 2.4 m spatial
resolution and PAN with 0.6 m spatial resolution.
I followed this procedure: 

- i.group to make a group with the RGB imagery
- make classes by digitizing polygons to identify the probably road and
no-road pixels
- i.gensingset to make the statistic and produce the signature file
- i.smap to classify
- r.mapcalc to extract the road class

First problem: with this method I can extract the roads
(approximately...) but I get many pixel too which are not road. I would
need to made a structural classification too. Maybe I should use
r.texture but I don't know exactly how.

Second problem: when I get finally a good classification, a simple
r.thin and r.to.vect would not be enough because the pixel are not all
close and precise on the lines, but are "scattered" along the line, so I
don't get a line but many little disordered lines along the road. Is
there a way to get a single and straight vector line in this conditions?

regards,
tommaso


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