[GRASSLIST:9090] Re: Raster-2-Vector Methodology Sugestions?

[Hamish]

> I have a scanned color topo map an would like to filter out the brown 
> topo lines from blue rivers/grid lines and black writing, then
> vectorize  them to have just a contour map.
> 
> So far I have not been very happy with the results.  And I was
> wondering  if anyone has had any good experience and could share their
> steps to get  good results.
> 
> I first ran i.cluster & i.maxlik, r.mapcalc to get the group that was 
> mainly the contours, r.thin , and then converted them to vector.


what about loading into the GIMP or similar, select -> by color, select
-> invert, edit-> cut, save. Then r.in.gdal, r.null, r.thin, r.contour
or r.to.vect.



Hamish