[GRASS-user] ascii to dem

[Glynn Clements]

antonio rodriguez wrote:

> The raster data is imported fine, but when trying to convert it to a 
> vector file:
> 
> r.to.vect in=bati3 out=bati3 
> 
> Extracting lines ...
> update_list: crowded cell 8H (1,2)
> ERROR:Raster map is not thinned properly.
>       Please run r.thin.
> 
> I do that, but:
> 
> r.thin in=bati3 out=bati3_thin
> 
> File bati3 -- 241 rows X 421 columns
> Bounding box: l = 2, r = 422, t = 2, b = 242
> Pass number 1
> Deleted 1320 pixels
> Pass number 2
> Deleted 1312 pixels
> Pass number 3
> Deleted 1304 pixels
> Pass number 4
> Deleted 1296 pixels
> 
> At the end of the process almost all the data were erased. What is 
> r.thin finding so wrong in my data that it deletes almost everything?

r.thin is appropriate if your raster data consists of lines, e.g. a
scanned contour map. It thins the lines so that they are only one cell
wide.

If you are trying to convert filled areas to vector areas, don't use
r.thin. You also need to pass feature=area to r.to.vect.

-- 
Glynn Clements <glynn at gclements.plus.com>