[Qgis-user] GEOPROCESSING: UNION of more polygons of different layers

[Andreas Neumann]

Hi Matthias,

Thanks for this useful hint.

But this "union" is also just a concatenating - it is in the sense of a 
union of SQL result sets. It does not create new geometries, as a 
geometric union would do.

So the question remains: what type of "union" does Azzurra want? a 
concatenation of several data sets or a geometric union where new 
geometries of overlapping features are generated?

Andreas

On 21.12.2015 14:10, Matthias Kuhn wrote:
> I have recently used OGR VRT for this:
>
> http://www.gdal.org/drv_vrt.html
> *OGRVRTUnionLayer*
>
> If you are not afraid of editing an XML file, that would be an approach.
>
> Matthias
>
>
> On 12/21/2015 01:37 PM, Andreas Neumann wrote:
>> Hi,
>>
>> Isnt' merge something else than union? As far as I know, merge only
>> copies the content of one layer into the other, whereas union really
>> unites overlapping geometry and creates new features. You'd have to
>> define how it handles the attributes.
>>
>> Andreas
>>
>> On 21.12.2015 11:49, Lewis Villierme wrote:
>>> Hi,
>>>
>>> There's a tool called in vector/Data management/Merges Multiples
>>> layer to one
>>>
>>> you can specify a folder in which you have all your shapefile to merge.
>>>
>>> regards.
>>>
>>> 2015-12-21 10:04 GMT+00:00 Azzurra Lentini <azzurralentini at gmail.com>:
>>>> Dear all,
>>>> is it possible in Qgis to do the union of more polygons of
>>>> differents layers
>>>> (so from more input layers to have one output layer as I can do in
>>>> arcgis)?
>>>>
>>>> In vector --> geoprocess --> union
>>>> is the union of only 2 different layers but is not possible a union
>>>> a more
>>>> of 2 layers.
>>>>
>>>> Thanks, Azzurra
>>>>
>>>> -- 
>>>> Dr. Hydrogeologist
>>>> AZZURRA LENTINI
>>>> Expert of evaluation environmental hazards
>>>> GIS application
>>>> Haity Mobile Tel: 0050946057393
>>>> ++++++++++++++++++++++++++
>>>> Italy Mobile Tel.: **(39) 338 24 40 676
>>>> ++++++++++++++++++++++++++
>>>> SKYPE azzurrahydro
>>>> ++++++++++++++++++++++++++
>>>> azzurralentini at gmail.com
>>>> ++++++++++++++++++++++++++
>>>> *Par respect pour l'environnement,*
>>>>
>>>> *n'imprimez ce mail qu'en cas d'absolue nécessité*
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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