[GRASS-user] v.clean tool=prune - 'thresh' interpreted wrong?

[Hamish]

Maciej Sieczka wrote:
> There is a line:
> 
> 	$ echo "L 4 1
> 	 10 10
> 	 20 10
> 	 30 10
> 	 40 10
> 	 1     1" | v.in.ascii -n out=line format=standard
> 
> 
> So there are 4 vertices and the distance between each 2 following is
> 10. Then I don't understand why the:
> 
> 	$ v.clean input=line output=line_pruned type=line tool=prune
> 	thresh=1
> 
> removes ALL the vertices!:
> 
> 	$ v.out.ascii line_pruned format=standard
> 	ORGANIZATION:
> 	DIGIT DATE:
> 	DIGIT NAME:   shoofi
> 	MAP NAME:
> 	MAP DATE:     Mon Oct  2 20:51:52 2006
> 	MAP SCALE:    1
> 	OTHER INFO:
> 	ZONE:         0
> 	MAP THRESH:   0.000000
> 	VERTI:
> 	L  2 1
> 	 10           10
> 	 40           10	   <- WHY ARE THE TWO OTHER GONE ???
> 	 1     1
> 
> 
> I declared thresh=1, the distance between vertices is 10 - so none
> should be removed, but all are! And the same happens with all the lower
> thresholds until thresh=0.03.
> 
> ???
> 
> v.clean man says: "prune: remove vertices in threshold". Maybe I don't
> understand what the threshold means in this case?


what if there is some angle between the points? e.g.

G6> v.in.ascii -n out=line format=standard << EOF
L 4 1
 10 10
 20 5
 30 7.5
 40 10
 1  1
EOF


Hamish