[GRASS-user] Help creating dissolved multipolygon

Roger_Andre · October 20, 2009, 8:37pm

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

M_S · October 20, 2009, 8:47pm

Is there output for the dissolve command?

Mark

On Oct 20, 2009, at 4:37 PM, Roger André <randre@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@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

Roger_Andre · October 20, 2009, 11:05pm

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@gmail.com> wrote:

Is there output for the dissolve command?

Mark

On Oct 20, 2009, at 4:37 PM, Roger André <randre@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@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

M_S · October 20, 2009, 11:24pm

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@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@gmail.com> wrote:

Is there output for the dissolve command?

Mark

On Oct 20, 2009, at 4:37 PM, Roger André <randre@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@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

Roger_Andre · October 21, 2009, 5:57pm

Yes, and in fact the PostGIS geomunion function uses the "diss" field
just fine to group by.
--

On Tue, Oct 20, 2009 at 4:24 PM, M S <mseibel@gmail.com> wrote:

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@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@gmail.com> wrote:

Is there output for the dissolve command?

Mark

On Oct 20, 2009, at 4:37 PM, Roger André <randre@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@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user