[GRASS-user] Tracing dotted lines from raster (and convert to vector)

[Nikos Alexandris]

> I have found that when you are working with discontinuous line segments that 
> don't have gaps too large -- it is possible to "re-connect" the lines with 
> the following procedure:
> 
> 1. extract only the color of interest
> 2. use r.grow to "fatten" the segments until they touch
> 3. use r.thin to return the segments to linear feature
> 4. vectorize with r.to.vect
> 
> I have used this approach with area features as well. See this link for some 
> ideas:
> http://casoilresource.lawr.ucdavis.edu/drupal/node/244
> 
> Cheers,
> 
> Dylan


Yep,

it works great. Also here
http://grass.osgeo.org/wiki/Trace_vector_contours_from_a_scanned_map

which might be yours ;-)

Thanks.

It feels good that I also "found" the same way more or less in the end.
I noticed the "trick" of keeping the color of the lines of interest
afterwards.