charlie wrote:
Hi. I am currently using Grass 6.4 on linux and beginning the the
process of vectorizing an old NOAA raster map with r.thin. The map is
approximately 12,000 pixels by 8,000 pixels wide.
According to this post, (
http://osgeo-org.1803224.n2.nabble.com/r-thin-td2718260.html#a2718260
)the iteration variable has to be equal or larger than half the number
of cells of the wider line so I increased the iterations to 6,000, and
it would up finishing in approximately 4,200 passes.
Previously, I was getting excellent preliminary results, with fewer
(1,000) iterations, distinct features were visible, however at least
50% of the map was not completed.
Now with an increase to 6,000 iterations r.thin completes, but the
results are a single 1px wide horizontal line. Im sure I am
overlooking something relatively simple; can anyone give me any advice
on how to best run r.thin in this particular case?
What is it you are trying to do? The r.thin module is designed to make
line features in a raster exactly one pixel wide so that when converting
to a line vector, the line will be clean.
If you run r.thin on a raster that represents areas, and give a high
enough iteration value, the areas will eventually be reduced to lines.
Thanks!
Charlie
<a href="www.wetlandresearch.com">Wetlands</a>
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