[GRASS-user] v.clean error threshold under 2 meters

[Markus Neteler]

On Tue, Apr 7, 2015 at 11:09 AM, Pierluigi De Rosa
<pierluigi.derosa at gfosservices.it> wrote:
> Dear all,
>
> I'm running under an XY location (uprojected).
> Could be this the problem?

Yes. While you *think* in meters, the GIS only knows "xy", i.e. no units.

> We are using a local zero not linked to any reference system.

Any chance to avoid that and use e.g. UTM?

> Here the output:
>
> g.proj -w
> XY location (unprojected)
>
>  g.region -p
> projection: 0 (x,y)
> zone:       0
> north:      1
> south:      0
> west:       0
> east:       1
> nsres:      0.0001
> ewres:      0.0001
> rows:       10000
> cols:       10000
> cells:      100000000
>
> This is the output of v.clean
> v.clean input=rill_800_parcellaB_polyline at pierluigi
> output=rill_800_parcellaB_prune tool=prune threshold=0.1

I am not sure at all how v.clean/the vector lib/any distance threshold
would work in a XY unprojected context. Probably not at all since
there is no reference.

Solution:
- create a new location with metric units
- import the data there

You can either leave them with 0,0 reference or move to the right
place using r.region (not g.region) or v.transform, respectively.
In a true metric context the thresholds will behave as expected.

Markus