polygon overlay

[sit]

Please,
If I have two polygons that overlap in a vector, how can I cut one of them on the border of the other (the clip function in arcview)?

Thank you

 

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[Giovanni Manghi]

On Sat, 2011-05-14 at 20:01 +0200, sit wrote:
> Please,
> If I have two polygons that overlap in a vector, how can I cut one of
> them on the border of the other (the clip function in arcview)?
> Thank you

vector->geoprocessing tools->clip

cheers

-- G --


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[Alister Hood]

> Date: Sun, 15 May 2011 02:45:06 +0100

> From: Giovanni Manghi <[hidden email]>
> Subject: Re: [Qgis-user] polygon overlay
> To: sit <[hidden email]>
> Cc: [hidden email]
> Message-ID: <1305423906.10867.1.camel@sibirica>
> Content-Type: text/plain; charset="UTF-8"
>
> On Sat, 2011-05-14 at 20:01 +0200, sit wrote:
> > Please,
> > If I have two polygons that overlap in a vector, how can I cut one of
> > them on the border of the other (the clip function in arcview)?
> > Thank you
>
> vector->geoprocessing tools->clip
>
> cheers
>
> -- G --
>
>
> ------------------------------
> Date: Sun, 15 May 2011 08:05:23 +0200
> From: Matteo Mura <[hidden email]>
> Subject: [Qgis-user] RE: polygon overlay (sit)
> To: [hidden email]
> Cc: [hidden email]
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset=us-ascii
>
> Hi
> first of all you should install the fTools plug-in, then from the menu bar: Vector > Geoprocessing tools > Clip
>
> input vector: vector to clip
> clip vector: vector which use  the boundary to make the clip
>
> i hope iwas useful, otherwise ask again
>
> Matteo

Hi everyone, I could be wrong, but I thought they were asking how to use an object to clip another object in the same layer.

Ftools can only use all the objects in a layer to clip all the objects in a different layer, producing a new layer.  This can obviously still be used to achieve the desired outcome, but it will require the use of several temporary files and copying and pasting objects between files.

It would be very nice if features like clipping were implemented kind of as advanced digitising features, so they could operate with/on selected features.  But I imagine this would need a reasonable amount of work from someone.


Alister

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[Giovanni Manghi]

Hi,


> Hi everyone, I could be wrong, but I thought they were asking
> how to use an object to clip another object in the same layer.

yes, as it resulted by an off list exchange with the original poster.


> Ftools can only use all the objects in a layer to clip all
> the objects in a different layer, producing a new layer.  
> This can obviously still be used to achieve the desired
> outcome, but it will require the use of several
> temporary files and copying and pasting objects between files.


right.



> It would be very nice if features like clipping were
> implemented kind of as advanced digitising features,
> so they could operate with/on selected features.
> But I imagine this would need a reasonable amount of work from someone.


the original problem was: "I have a polygon vector and sometimes I add
to it new polygons, but not digitizing them, for example downloading
tracks from a GPS. The new polygon obviously will not be perfectly
adjacent to the existing one and I need a tool that clips (and fill)
where needed (the new polygon)."

Using the "avoid intersection of new polygons" and the "reshape tool" it
can be done, but it is bit tricky, especially if the "common" border has
a lot of nodes.

I agree that a ad hoc tool would be better.

Cheers

-- Giovanni --


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[sit]

Hi everyone and thanks,

my problems in polygons overlapping is very important; I'm a botanist and I go in field to collect with a GPS a lot of polygons that have variations on border; I speak of about 50-100 polygons for kmq in a semester; in the "stupid" arcgis, it is very simple to paste the new polygons to the existing shape and then (with a function called clip but in the editing mask of the same shape, not beetween two files) placing them with the new border, avoiding overlapping.
I'm tryng to convince my colleagues to use Q-Gis, but if this simple operation is not possible, a lot of them will not use: no one can reshape by hand a lot of polygons already collect with GPS or updated by some new administration!!

 

Please help me

 

S.

 

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Gestione Riserve Naturali

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Da: [hidden email]

A: [hidden email]

Cc:

Data: Mon, 16 May 2011 00:19:11 +1200

Oggetto: [Qgis-user] RE: polygon overlay

> > Date: Sun, 15 May 2011 02:45:06 +0100

> > From: Giovanni Manghi

> > Subject: Re: [Qgis-user] polygon overlay

> > To: sit

> > Cc: [hidden email]

> > Message-ID: <1305423906.10867.1.camel@sibirica>

> > Content-Type: text/plain; charset="UTF-8"

> >

> > On Sat, 2011-05-14 at 20:01 +0200, sit wrote:

> > > Please,

> > > If I have two polygons that overlap in a vector, how can I cut one of

> > > them on the border of the other (the clip function in arcview)?

> > > Thank you

> >

> > vector->geoprocessing tools->clip

> >

> > cheers

> >

> > -- G --

> >

> >

> > ------------------------------

> > Date: Sun, 15 May 2011 08:05:23 +0200

> > From: Matteo Mura

> > Subject: [Qgis-user] RE: polygon overlay (sit)

> > To: [hidden email]

> > Cc: [hidden email]

> > Message-ID: <[hidden email]>

> > Content-Type: text/plain; charset=us-ascii

> >

> > Hi

> > first of all you should install the fTools plug-in, then from the menu bar: Vector > Geoprocessing tools > Clip

> >

> > input vector: vector to clip

> > clip vector: vector which use the boundary to make the clip

> >

> > i hope iwas useful, otherwise ask again

> >

> > Matteo

>

> Hi everyone, I could be wrong, but I thought they were asking how to use an object to clip another object in the same layer.

>

> Ftools can only use all the objects in a layer to clip all the objects in a different layer, producing a new layer. This can obviously still be used to achieve the desired outcome, but it will require the use of several temporary files and copying and pasting objects between files.

>

> It would be very nice if features like clipping were implemented kind of as advanced digitising features, so they could operate with/on selected features. But I imagine this would need a reasonable amount of work from someone.

>

>

> Alister

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[Giovanni Manghi]

Hi,

> I'm tryng to convince my colleagues to use Q-Gis, but if this simple
> operation is not possible, a lot of them will not use: no one can
> reshape by hand a lot of polygons already collect with GPS or updated
> by some new administration!!

if I understand the problem is possible by using the "avoid intersection
of new polygons" and the "reshape tool" in the standard editing toolbox.

It can be tricky but it works.

Please check if it works for you.


Cheers

-- Giovanni --

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[Paolo Cavallini]

Il 15/05/2011 21:30, sit ha scritto:

> my problems in polygons overlapping is very important; I'm a botanist and I go in
> field to collect with a GPS a lot of polygons that have variations on border; I speak
> of about 50-100 polygons for kmq in a semester; in the "stupid" arcgis, it is very
> simple to paste the new polygons to the existing shape and then (with a function
> called clip but in the editing mask of the same shape, not beetween two files)
> placing them with the new border, avoiding overlapping.
> I'm tryng to convince my colleagues to use Q-Gis, but if this simple operation is not
> possible, a lot of them will not use: no one can reshape by hand a lot of polygons
> already collect with GPS or updated by some new administration!!

Agreed, this would be useful. The good news is that it is also quite feasible. Anyone
interested in sponsoring its development?
All the best.

--
Paolo Cavallini: http://www.faunalia.it/pc
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[Andrea Peri]

Il 15/05/2011 21:30, sit ha scritto:

> my problems in polygons overlapping is very important; I'm a botanist and I go in
> field to collect with a GPS a lot of polygons that have variations on border; I speak

> of about 50-100 polygons for kmq in a semester; in the "stupid" arcgis, it is very
> simple to paste the new polygons to the existing shape and then (with a function
> called clip but in the editing mask of the same shape, not beetween two files)

> placing them with the new border, avoiding overlapping.
> I'm tryng to convince my colleagues to use Q-Gis, but if this simple operation is not
> possible, a lot of them will not use: no one can reshape by hand a lot of polygons

> already collect with GPS or updated by some new administration!!

I understand you would load directly from GPS without any human action,
so starting from an empty dataset.
You load the first polygon, after loading the second polygon you like it would be changed accordly to the first polygon,
after loading another polygon you like it would be changed accordly with the first and the second polygons, and so on...

This could be work if the GPS is a really good differentially gps, and not a simple hobbist GPS because it could change
the polygon due to man environmental situation (rain, fog, etc..) and could be happened the third polygon is good meanwhile the first and the second are not so quality good.


--
-----------------
Andrea Peri
. . . . . . . . .
qwerty àèìòù
-----------------


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[Sr. Neto]

I guess implementing topology rules and visualizing the existing errors would be a way to identify and correct problems like polygon overlaping.

It might already exist some code.

http://www.osgeo.org/pipermail/qgis-developer/2010-January/009011.html

Too bad I'm not a programmer... :-(

On Mon, May 16, 2011 at 8:54 AM, Paolo Cavallini <[hidden email]> wrote:

Il 15/05/2011 21:30, sit ha scritto:

> my problems in polygons overlapping is very important; I'm a botanist and I go in
> field to collect with a GPS a lot of polygons that have variations on border; I speak
> of about 50-100 polygons for kmq in a semester; in the "stupid" arcgis, it is very
> simple to paste the new polygons to the existing shape and then (with a function
> called clip but in the editing mask of the same shape, not beetween two files)
> placing them with the new border, avoiding overlapping.
> I'm tryng to convince my colleagues to use Q-Gis, but if this simple operation is not
> possible, a lot of them will not use: no one can reshape by hand a lot of polygons
> already collect with GPS or updated by some new administration!!

Agreed, this would be useful. The good news is that it is also quite feasible. Anyone
interested in sponsoring its development?
All the best.

--
Paolo Cavallini: http://www.faunalia.it/pc

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