[GRASS-user] Help creating dissolved multipolygon

[M S]

If you query two adjacent polygons, do they both have the same value
for the 'diss' attribute?

On Tue, Oct 20, 2009 at 7:05 PM, Roger André <randre at gmail.com> wrote:
> Yeah, kinda long, but here it is.  fwiw, I loaded the file into
> PostGIS and let it crank away at the dissolve.  Was done after about
> an hour, so while I'm thrilled to have the correct data, I'd still
> like to figure out a solution in GRASS.
>
>> v.dissolve global_mask out=new_mask col=diss --o
>  100%
> Building topology for vector map <new_mask_18169>...
> Registering primitives...
> 5450 primitives registered
> 288073 vertices registered
> Building areas...
>  100%
> 2723 areas built
> 2721 isles built
> Attaching islands...
>  100%
> Attaching centroids...
>  100%
> Number of nodes: 5448
> Number of primitives: 5450
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 2727
> Number of centroids: 2723
> Number of areas: 2723
> Number of isles: 2721
> v.reclass complete. 2723 features reclassed.
> WARNING: Vector map <new_mask> already exists and will be overwritten
> Extracting features...
> Building topology for vector map <new_mask>...
> Registering primitives...
> 5450 primitives registered
> 288073 vertices registered
> Building areas...
>  100%
> 2723 areas built
> 2721 isles built
> Attaching islands...
>  100%
> Attaching centroids...
>  100%
> Number of nodes: 5448
> Number of primitives: 5450
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 2727
> Number of centroids: 2723
> Number of areas: 2723
> Number of isles: 2721
> Writing attributes...
> Removing duplicate centroids...
> Building topology for vector map <new_mask>...
> Registering primitives...
> 5450 primitives registered
> 288073 vertices registered
> Building areas...
>  100%
> 2723 areas built
> 2721 isles built
> Attaching islands...
>  100%
> Attaching centroids...
>  100%
> Number of nodes: 5448
> Number of primitives: 5450
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 2727
> Number of centroids: 2723
> Number of areas: 2723
> Number of isles: 2721
>
>
> On Tue, Oct 20, 2009 at 1:47 PM, MS <mseibel at gmail.com> wrote:
>> Is there output for the dissolve command?
>>
>> Mark
>>
>> On Oct 20, 2009, at 4:37 PM, Roger André <randre at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> I'm having trouble creating a single, dissolved feature and exporting
>>> it as a multipolygon.  Here is what I've done:
>>>
>>> - layer I started with:
>>>>
>>>> v.info -t global_mask
>>>
>>> nodes=5448
>>> points=0
>>> lines=0
>>> boundaries=2727
>>> centroids=2723
>>> areas=2723
>>> islands=2721
>>> faces=0
>>> kernels=0
>>> primitives=5450
>>> map3d=0
>>>
>>> - added dissolve field:
>>>>
>>>> v.db.addcol global_mask col="diss int"
>>>> v.db.update global_mask col=diss value=1
>>>
>>> - check that diss field is there:
>>>>
>>>> v.info -c global_mask
>>>
>>> Displaying column types/names for database connection of layer 1:
>>> INTEGER|cat
>>> DOUBLE PRECISION|cat_
>>> INTEGER|diss
>>>
>>> - dissolve:
>>> v.dissolve global_mask out=new_mask col=diss --o
>>>
>>> - inspect new layer:
>>>>
>>>> v.info -t new_mask
>>>
>>> nodes=5448
>>> points=0
>>> lines=0
>>> boundaries=2727
>>> centroids=2723
>>> areas=2723
>>> islands=2721
>>> faces=0
>>> kernels=0
>>> primitives=5450
>>> map3d=0
>>>
>>> - export layer as shapefile:
>>>>
>>>> v.out.ogr -p input=new_mask type=area dsn=/tmp olayer=new_mask
>>>
>>> - check new shapefile:
>>> ogrinfo -summary /tmp new_mask
>>> INFO: Open of `/tmp'
>>>     using driver `ESRI Shapefile' successful.
>>>
>>> Layer name: new_mask
>>> Geometry: Polygon
>>> Feature Count: 2723
>>> Extent: (-180.000000, -90.000000) - (180.000000, 83.623596)
>>> Layer SRS WKT:
>>> GEOGCS["GCS_WGS_1984",
>>>   DATUM["WGS_1984",
>>>       SPHEROID["WGS_1984",6378137,298.257223563]],
>>>   PRIMEM["Greenwich",0],
>>>   UNIT["Degree",0.017453292519943295]]
>>> cat: Real (11.0)
>>>
>>> As you can see, I still have 2723 features, when I expect to have 1.
>>>
>>> What am I doing wrong?
>>>
>>> Roger
>>> _______________________________________________
>>> grass-user mailing list
>>> grass-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/grass-user
>>
>