[GRASS-user] Help creating dissolved multipolygon

[Roger André]

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
>