[GRASS-user] Help creating dissolved multipolygon

[Roger André]

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