[GRASS-user] eliminate some lines

GRASS GRASS user
1

/*hello

I couldn't do with v.clean what I wanted to do.
I want to eliminate all lines whose their langth are under 20 m.

what is the solution ?

regards
*/

--
Ahmet Temiz

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2

temiz wrote:

/*hello

I couldn't do with v.clean what I wanted to do.
I want to eliminate all lines whose their langth are under 20 m.

what is the solution ?

not tested:

v.to.db map=Original option=length type=line col=linelength units=me
v.extract input=Original output=Original20 where="linelength>20"

Moritz

3

On Thu, Nov 02, 2006 at 10:24:49AM -0500, temiz wrote:

/*hello

I couldn't do with v.clean what I wanted to do.
I want to eliminate all lines whose their langth are under 20 m.

what is the solution ?

regards
*/

You could add a new column with v.db.addcol and then
upload the vector line lengths to this column with
v.to.db and option=length.
Then use v.extract with a simple SQL rule to extract
all but lengths < 20m.

Markus

4

Moritz Lennert wrote:

temiz wrote:

/*hello

I couldn't do with v.clean what I wanted to do.
I want to eliminate all lines whose their langth are under 20 m.

what is the solution ?

not tested:

v.to.db map=Original option=length type=line col=linelength units=me
v.extract input=Original output=Original20 where="linelength>20"

Moritz

thank you Moritz and Markus

I solved this problem ( grass is really capable).

When I looked at v.to.db, I thought whether I could calculate
the "length of a polygon" as well.

Do you have idea ?

thanks again

--
Ahmet Temiz

--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

5

temiz wrote:

Moritz Lennert wrote:

temiz wrote:

/*hello

I couldn't do with v.clean what I wanted to do.
I want to eliminate all lines whose their langth are under 20 m.

what is the solution ?

not tested:

v.to.db map=Original option=length type=line col=linelength units=me
v.extract input=Original output=Original20 where="linelength>20"

Moritz

thank you Moritz and Markus

I solved this problem ( grass is really capable).

When I looked at v.to.db, I thought whether I could calculate
the "length of a polygon" as well.

Depends on the polygon. If it defined as a boundary, then try setting
type=boundary and option=length

If it is an area then type=area and option=perimeter

Moritz

6

Moritz Lennert wrote:

> When I looked at v.to.db, I thought whether I could calculate
> the "length of a polygon" as well.

Depends on the polygon. If it defined as a boundary, then try setting
type=boundary and option=length

If it is an area then type=area and option=perimeter

note "v.clean tool=rmarea thresh=.. " is prefered for removing small
areas, as polygon boundary length is a fractal problem.

Hamish