[GRASS-user] v.clean error threshold under 2 meters
Markus Neteler
neteler at osgeo.org
Tue Apr 7 05:41:34 PDT 2015
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
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