[Qgis-user] Shape file - Change "Polygon" to "Multipolygon"

[Andrea Giudiceandrea]

Hi Riccardo,
have you managed to solve your issue?

Best regards.

Andrea

Il 27/04/2023 20:46, Andrea Giudiceandrea ha scritto:
>> Riccardo riccardopani at hotmail.com
>> Thu Apr 27 03:06:54 PDT 2023
> 
>> I have shape file already created for a standard delivery.
>> The geometry type of this shape file is “Polygon” and I have to change 
>> it into “Multipolygon”.
>> Is it possible? And how can I change this property in a shape file 
>> already created without creating a new one?
> 
> Hi Riccardo,
> if with "shape file" you are referring to the ESRI Shapefile format, 
> then, as you can read in the "ESRI Shapefile Technical Description" [1], 
> there is only one type of polygon layer (apart from the M and Z+M 
> variants) in the ESRI Shapefile format: it is called Polygon in the 
> format nomenclature and it can stores natively both multi-part and 
> single-part (which are actually multipart with only 1 part) geometries.
> 
> An ESRI Shapefile Polygon layer is imported in QGIS (at least, for 
> recent versions) as a "Polygon (MultiPolygon)" layer, i.e. a 
> MultiPolygon layer, even if it does not contains any feature or if only 
> contains geometries with only 1 part.
> 
> In QGIS, any geometry contained in an ESRI Shapefile Polygon layer is 
> considered a MultiPolygon geometry: if it has only 1 part, it will be a 
> MultiPolygon geometry with only one part; if it has more then 1 part, it 
> will be a MultiPolygon with more than 1 part.
> 
> Is your "shape layer" an ESRI Shapefile layer? If yes, could you better 
> explain why do you think the geometry type of this "shape file" is (non 
> Multi) "Polygon". If not, could you please name the format of the layer?
> 
> Best regards.
> 
> Andrea Giudiceandrea
> 
> [1] 
> https://www.esri.com/content/dam/esrisites/sitecore-archive/Files/Pdfs/library/whitepapers/pdfs/shapefile.pdf#page=12