[GRASS-user] Help creating dissolved multipolygon

[MS]

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
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