[GRASS-user] Spatial Dissolve

GRASS GRASS user
,
1

Hi all,

I'm new to GRASS, and using it in Windows via QGIS.

I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
attribute, but rather just remove unnecessary tile boundaries) on a
file that I've imported to GRASS from a shapefile, and am so far
unsuccessful. The file contains waterbodies, and some of them are cut
in pieces by tile boundaries. I would like to remove these
boundaries. Can someone please help me out? I've tried combinations
of v.extract -d with no success, and am not sure how the "category"
value apply when I'm not dissolving on an attribute.

So far my search of the archives has turned up something close, but
nothing that seems to fit my situation exactly.

Cheers,

Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

2

Hi Darren,

I also stumbled over this problem, but we solved it. The trick is that
you first have to remove the duplicated tile boundaries, then dissolve
works.
See example for CORINE Landcover SHAPE files:
http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html

Cheers
Markus

Darren Cope wrote:

Hi all,

I'm new to GRASS, and using it in Windows via QGIS.

I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
attribute, but rather just remove unnecessary tile boundaries) on a
file that I've imported to GRASS from a shapefile, and am so far
unsuccessful. The file contains waterbodies, and some of them are cut
in pieces by tile boundaries. I would like to remove these
boundaries. Can someone please help me out? I've tried combinations
of v.extract -d with no success, and am not sure how the "category"
value apply when I'm not dissolving on an attribute.

So far my search of the archives has turned up something close, but
nothing that seems to fit my situation exactly.

Cheers,

Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

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3

Hi Markus,

I must be missing something, because this still does not seem to work.
I found another (non-GRASS) way to accomplish this, so the priority
is not very high, but I'd still like to figure out the GRASS method.
Is the v.patch step in the CORINE example necessary, or mostly just
the v.clean step with rmdupl?

Cheers,

Darren

On 5/16/07, Markus Neteler <neteler@itc.it> wrote:

Hi Darren,

I also stumbled over this problem, but we solved it. The trick is that
you first have to remove the duplicated tile boundaries, then dissolve
works.
See example for CORINE Landcover SHAPE files:
http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html

Cheers
Markus

Darren Cope wrote:
>
> Hi all,
>
> I'm new to GRASS, and using it in Windows via QGIS.
>
> I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
> attribute, but rather just remove unnecessary tile boundaries) on a
> file that I've imported to GRASS from a shapefile, and am so far
> unsuccessful. The file contains waterbodies, and some of them are cut
> in pieces by tile boundaries. I would like to remove these
> boundaries. Can someone please help me out? I've tried combinations
> of v.extract -d with no success, and am not sure how the "category"
> value apply when I'm not dissolving on an attribute.
>
> So far my search of the archives has turned up something close, but
> nothing that seems to fit my situation exactly.
>
> Cheers,
>
> Darren Cope
> darrencope@gmail.com
> http://dmcope.freeshell.org
>
> _______________________________________________
> grassuser mailing list
> grassuser@grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser
>

--
View this message in context: http://www.nabble.com/Spatial-Dissolve-tf3758601.html#a10642373
Sent from the Grass - Users mailing list archive at Nabble.com.

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

--
Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

4

Darren,

could you be more specific about what you did (commands + flags/params),
which GRASS version etc? I just used this method recently again with
success.
The v.patch step in the CORINE example is necessary for *CORINE* since
you get vector tiles. If you have already a patched map, don't use it.

Markus

Darren Cope wrote on 05/28/2007 02:01 PM:

Hi Markus,

I must be missing something, because this still does not seem to work.
I found another (non-GRASS) way to accomplish this, so the priority
is not very high, but I'd still like to figure out the GRASS method.
Is the v.patch step in the CORINE example necessary, or mostly just
the v.clean step with rmdupl?

Cheers,

Darren

On 5/16/07, Markus Neteler <neteler@itc.it> wrote:

Hi Darren,

I also stumbled over this problem, but we solved it. The trick is that
you first have to remove the duplicated tile boundaries, then dissolve
works.
See example for CORINE Landcover SHAPE files:
http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html

Cheers
Markus

Darren Cope wrote:
>
> Hi all,
>
> I'm new to GRASS, and using it in Windows via QGIS.
>
> I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
> attribute, but rather just remove unnecessary tile boundaries) on a
> file that I've imported to GRASS from a shapefile, and am so far
> unsuccessful. The file contains waterbodies, and some of them are cut
> in pieces by tile boundaries. I would like to remove these
> boundaries. Can someone please help me out? I've tried combinations
> of v.extract -d with no success, and am not sure how the "category"
> value apply when I'm not dissolving on an attribute.
>
> So far my search of the archives has turned up something close, but
> nothing that seems to fit my situation exactly.
>
> Cheers,
>
> Darren Cope
> darrencope@gmail.com
> http://dmcope.freeshell.org

------------------
ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler
------------------

5

Hi Markus and list,

- I'm using GRASS 6.3.cvs (2006) underQGIS (using the
qgis_setup0.8.1preview3.exe installer from:
http://qgis.org/uploadfiles/testbuilds/) in a Windows 2000
environment. I've installed qgis in a directory (C:\QGIS) with no
spaces or path names over 8 characters
- the data I downloaded is from the geographynetwork.ca website, and
comes in shapefile format
- Created a new mapset in GRASS (using QGIS GUI)
- Added shapefile to QGIS project
- import shapefile to GRASS vector using v.in.ogr using QGIS "GRASS Tools"
- run v.clean as per CORINE example (v.clean input=wateroriginal
output=waterclean tool=rmdupl) in GRASS shell
- at this point I noticed that the attribute values are not carried
through and I'm left with only "id" and "cat" - why is this, and will
it cause problems later on?
- run v.dissolve (v.dissolve input=waterclean output=waterdissolve) in
GRASS shell, result is a non-dissolved file - I didn't specify a
category, but I'm only doing a "spatial" dissolve, so is this
necessary?
- I also tried v.extract -d (v.extract -d input=waterclean
output=waterextract) in the GRASS shell without success

Hopefully I'm missing something obvious! Any help would be appreciated.

Cheers,

Darren

On 5/28/07, Markus Neteler <neteler@itc.it> wrote:

Darren,

could you be more specific about what you did (commands + flags/params),
which GRASS version etc? I just used this method recently again with
success.
The v.patch step in the CORINE example is necessary for *CORINE* since
you get vector tiles. If you have already a patched map, don't use it.

Markus

Darren Cope wrote on 05/28/2007 02:01 PM:
> Hi Markus,
>
> I must be missing something, because this still does not seem to work.
> I found another (non-GRASS) way to accomplish this, so the priority
> is not very high, but I'd still like to figure out the GRASS method.
> Is the v.patch step in the CORINE example necessary, or mostly just
> the v.clean step with rmdupl?
>
> Cheers,
>
> Darren
>
> On 5/16/07, Markus Neteler <neteler@itc.it> wrote:
>>
>> Hi Darren,
>>
>> I also stumbled over this problem, but we solved it. The trick is that
>> you first have to remove the duplicated tile boundaries, then dissolve
>> works.
>> See example for CORINE Landcover SHAPE files:
>> http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html
>>
>> Cheers
>> Markus
>>
>> Darren Cope wrote:
>> >
>> > Hi all,
>> >
>> > I'm new to GRASS, and using it in Windows via QGIS.
>> >
>> > I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
>> > attribute, but rather just remove unnecessary tile boundaries) on a
>> > file that I've imported to GRASS from a shapefile, and am so far
>> > unsuccessful. The file contains waterbodies, and some of them are cut
>> > in pieces by tile boundaries. I would like to remove these
>> > boundaries. Can someone please help me out? I've tried combinations
>> > of v.extract -d with no success, and am not sure how the "category"
>> > value apply when I'm not dissolving on an attribute.
>> >
>> > So far my search of the archives has turned up something close, but
>> > nothing that seems to fit my situation exactly.
>> >
>> > Cheers,
>> >
>> > Darren Cope
>> > darrencope@gmail.com
>> > http://dmcope.freeshell.org

------------------
ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler
------------------

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

--
Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

6

Hi Darren,

On Mon, May 28, 2007 at 09:52:59PM -0400, Darren Cope wrote:

Hi Markus and list,

- I'm using GRASS 6.3.cvs (2006) underQGIS (using the
qgis_setup0.8.1preview3.exe installer from:
http://qgis.org/uploadfiles/testbuilds/) in a Windows 2000
environment.

[ I guess we still don't know which GRASS version they
  package :frowning: I even filed a bug report there to figure out,
  now way...
]

I've installed qgis in a directory (C:\QGIS) with no
spaces or path names over 8 characters
- the data I downloaded is from the geographynetwork.ca website, and
comes in shapefile format
- Created a new mapset in GRASS (using QGIS GUI)
- Added shapefile to QGIS project
- import shapefile to GRASS vector using v.in.ogr using QGIS "GRASS Tools"
- run v.clean as per CORINE example (v.clean input=wateroriginal
output=waterclean tool=rmdupl) in GRASS shell

Well, the example is a bit different:

http://grass.itc.it/gdp/html_grass63/v.dissolve.html
# remove duplicated tile boundaries:
v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl thresh=.01

# dissolve based on column attributes:
v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00

Please note that you need tool=snap,break,rmdupl, otherwise it won't
work. Attributes should survive (they do for me in various maps).

- at this point I noticed that the attribute values are not carried
through and I'm left with only "id" and "cat" - why is this, and will
it cause problems later on?

The problem originates from the incomplete v.clean call, I guess.

- run v.dissolve (v.dissolve input=waterclean output=waterdissolve) in
GRASS shell, result is a non-dissolved file - I didn't specify a
category, but I'm only doing a "spatial" dissolve, so is this
necessary?
- I also tried v.extract -d (v.extract -d input=waterclean
output=waterextract) in the GRASS shell without success

Hopefully I'm missing something obvious! Any help would be appreciated.

Please try again and let us know where you found the misleading
documentation (so that we can fix it).

Good luck,
Markus

Cheers,

Darren

On 5/28/07, Markus Neteler <neteler@itc.it> wrote:
> Darren,
>
> could you be more specific about what you did (commands + flags/params),
> which GRASS version etc? I just used this method recently again with
> success.
> The v.patch step in the CORINE example is necessary for *CORINE* since
> you get vector tiles. If you have already a patched map, don't use it.
>
> Markus
>
> Darren Cope wrote on 05/28/2007 02:01 PM:
> > Hi Markus,
> >
> > I must be missing something, because this still does not seem to work.
> > I found another (non-GRASS) way to accomplish this, so the priority
> > is not very high, but I'd still like to figure out the GRASS method.
> > Is the v.patch step in the CORINE example necessary, or mostly just
> > the v.clean step with rmdupl?
> >
> > Cheers,
> >
> > Darren
> >
> > On 5/16/07, Markus Neteler <neteler@itc.it> wrote:
> >>
> >> Hi Darren,
> >>
> >> I also stumbled over this problem, but we solved it. The trick is that
> >> you first have to remove the duplicated tile boundaries, then dissolve
> >> works.
> >> See example for CORINE Landcover SHAPE files:
> >> http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html
> >>
> >> Cheers
> >> Markus
> >>
> >>
> >> Darren Cope wrote:
> >> >
> >> > Hi all,
> >> >
> >> > I'm new to GRASS, and using it in Windows via QGIS.
> >> >
> >> > I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
> >> > attribute, but rather just remove unnecessary tile boundaries) on a
> >> > file that I've imported to GRASS from a shapefile, and am so far
> >> > unsuccessful. The file contains waterbodies, and some of them are cut
> >> > in pieces by tile boundaries. I would like to remove these
> >> > boundaries. Can someone please help me out? I've tried combinations
> >> > of v.extract -d with no success, and am not sure how the "category"
> >> > value apply when I'm not dissolving on an attribute.
> >> >
> >> > So far my search of the archives has turned up something close, but
> >> > nothing that seems to fit my situation exactly.
> >> >
> >> > Cheers,
> >> >
> >> > Darren Cope
> >> > darrencope@gmail.com
> >> > http://dmcope.freeshell.org
>
>
> ------------------
> ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
> ITC -> since 1 March 2007 Fondazione Bruno Kessler
> ------------------
>
> _______________________________________________
> grassuser mailing list
> grassuser@grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser
>

--
Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

7

Darren Cope ha scritto:

Hi Markus and list,

- I'm using GRASS 6.3.cvs (2006) underQGIS (using the
qgis_setup0.8.1preview3.exe installer from:
http://qgis.org/uploadfiles/testbuilds/) in a Windows 2000
environment. I've installed qgis in a directory (C:\QGIS) with no
spaces or path names over 8 characters
- the data I downloaded is from the geographynetwork.ca website, and
comes in shapefile format
- Created a new mapset in GRASS (using QGIS GUI)
- Added shapefile to QGIS project
- import shapefile to GRASS vector using v.in.ogr using QGIS "GRASS
Tools"
- run v.clean as per CORINE example (v.clean input=wateroriginal
output=waterclean tool=rmdupl) in GRASS shell
- at this point I noticed that the attribute values are not carried
through and I'm left with only "id" and "cat" - why is this, and will
it cause problems later on?

See the output message of v.in.ogr, maybe there is some problems in the
structure of the input table

- run v.dissolve (v.dissolve input=waterclean output=waterdissolve) in
GRASS shell, result is a non-dissolved file - I didn't specify a
category, but I'm only doing a "spatial" dissolve, so is this
necessary?

I see this bug with v.dissolve that is present only in grass 6.3

- I also tried v.extract -d (v.extract -d input=waterclean
output=waterextract) in the GRASS shell without success

Here you must specify the category list that you want extract or a query

Ciao
leonardo

Hopefully I'm missing something obvious! Any help would be appreciated.

Cheers,

Darren

On 5/28/07, Markus Neteler <neteler@itc.it> wrote:

Darren,

could you be more specific about what you did (commands + flags/params),
which GRASS version etc? I just used this method recently again with
success.
The v.patch step in the CORINE example is necessary for *CORINE* since
you get vector tiles. If you have already a patched map, don't use it.

Markus

Darren Cope wrote on 05/28/2007 02:01 PM:
> Hi Markus,
>
> I must be missing something, because this still does not seem to work.
> I found another (non-GRASS) way to accomplish this, so the priority
> is not very high, but I'd still like to figure out the GRASS method.
> Is the v.patch step in the CORINE example necessary, or mostly just
> the v.clean step with rmdupl?
>
> Cheers,
>
> Darren
>
> On 5/16/07, Markus Neteler <neteler@itc.it> wrote:
>>
>> Hi Darren,
>>
>> I also stumbled over this problem, but we solved it. The trick is
that
>> you first have to remove the duplicated tile boundaries, then
dissolve
>> works.
>> See example for CORINE Landcover SHAPE files:
>> http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html
>>
>> Cheers
>> Markus
>>
>>
>> Darren Cope wrote:
>> >
>> > Hi all,
>> >
>> > I'm new to GRASS, and using it in Windows via QGIS.
>> >
>> > I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
>> > attribute, but rather just remove unnecessary tile boundaries) on a
>> > file that I've imported to GRASS from a shapefile, and am so far
>> > unsuccessful. The file contains waterbodies, and some of them
are cut
>> > in pieces by tile boundaries. I would like to remove these
>> > boundaries. Can someone please help me out? I've tried
combinations
>> > of v.extract -d with no success, and am not sure how the "category"
>> > value apply when I'm not dissolving on an attribute.
>> >
>> > So far my search of the archives has turned up something close, but
>> > nothing that seems to fit my situation exactly.
>> >
>> > Cheers,
>> >
>> > Darren Cope
>> > darrencope@gmail.com
>> > http://dmcope.freeshell.org

------------------
ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler
------------------

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

8

On Tue, May 29, 2007 at 05:23:42PM +0200, Leonardo Lami wrote:

Darren Cope ha scritto:
> Hi Markus and list,
>
> - I'm using GRASS 6.3.cvs (2006) underQGIS (using the
> qgis_setup0.8.1preview3.exe installer from:
> http://qgis.org/uploadfiles/testbuilds/) in a Windows 2000
> environment. I've installed qgis in a directory (C:\QGIS) with no
> spaces or path names over 8 characters
> - the data I downloaded is from the geographynetwork.ca website, and
> comes in shapefile format
> - Created a new mapset in GRASS (using QGIS GUI)
> - Added shapefile to QGIS project
> - import shapefile to GRASS vector using v.in.ogr using QGIS "GRASS
> Tools"
> - run v.clean as per CORINE example (v.clean input=wateroriginal
> output=waterclean tool=rmdupl) in GRASS shell
> - at this point I noticed that the attribute values are not carried
> through and I'm left with only "id" and "cat" - why is this, and will
> it cause problems later on?
See the output message of v.in.ogr, maybe there is some problems in the
structure of the input table
> - run v.dissolve (v.dissolve input=waterclean output=waterdissolve) in
> GRASS shell, result is a non-dissolved file - I didn't specify a
> category, but I'm only doing a "spatial" dissolve, so is this
> necessary?
I see this bug with v.dissolve that is present only in grass 6.3

I don't think that it is a bug. If there are duplicated boundaries,
v.dissolve must fail.

(see also my other mail how to solve this)

Markus

> - I also tried v.extract -d (v.extract -d input=waterclean
> output=waterextract) in the GRASS shell without success
Here you must specify the category list that you want extract or a query

Ciao
leonardo
>
> Hopefully I'm missing something obvious! Any help would be appreciated.
>
> Cheers,
>
> Darren
>
> On 5/28/07, Markus Neteler <neteler@itc.it> wrote:
>> Darren,
>>
>> could you be more specific about what you did (commands + flags/params),
>> which GRASS version etc? I just used this method recently again with
>> success.
>> The v.patch step in the CORINE example is necessary for *CORINE* since
>> you get vector tiles. If you have already a patched map, don't use it.
>>
>> Markus
>>
>> Darren Cope wrote on 05/28/2007 02:01 PM:
>> > Hi Markus,
>> >
>> > I must be missing something, because this still does not seem to work.
>> > I found another (non-GRASS) way to accomplish this, so the priority
>> > is not very high, but I'd still like to figure out the GRASS method.
>> > Is the v.patch step in the CORINE example necessary, or mostly just
>> > the v.clean step with rmdupl?
>> >
>> > Cheers,
>> >
>> > Darren
>> >
>> > On 5/16/07, Markus Neteler <neteler@itc.it> wrote:
>> >>
>> >> Hi Darren,
>> >>
>> >> I also stumbled over this problem, but we solved it. The trick is
>> that
>> >> you first have to remove the duplicated tile boundaries, then
>> dissolve
>> >> works.
>> >> See example for CORINE Landcover SHAPE files:
>> >> http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html
>> >>
>> >> Cheers
>> >> Markus
>> >>
>> >>
>> >> Darren Cope wrote:
>> >> >
>> >> > Hi all,
>> >> >
>> >> > I'm new to GRASS, and using it in Windows via QGIS.
>> >> >
>> >> > I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
>> >> > attribute, but rather just remove unnecessary tile boundaries) on a
>> >> > file that I've imported to GRASS from a shapefile, and am so far
>> >> > unsuccessful. The file contains waterbodies, and some of them
>> are cut
>> >> > in pieces by tile boundaries. I would like to remove these
>> >> > boundaries. Can someone please help me out? I've tried
>> combinations
>> >> > of v.extract -d with no success, and am not sure how the "category"
>> >> > value apply when I'm not dissolving on an attribute.
>> >> >
>> >> > So far my search of the archives has turned up something close, but
>> >> > nothing that seems to fit my situation exactly.
>> >> >
>> >> > Cheers,
>> >> >
>> >> > Darren Cope
>> >> > darrencope@gmail.com
>> >> > http://dmcope.freeshell.org
>>
>>
>> ------------------
>> ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
>> ITC -> since 1 March 2007 Fondazione Bruno Kessler
>> ------------------
>>
>> _______________________________________________
>> grassuser mailing list
>> grassuser@grass.itc.it
>> http://grass.itc.it/mailman/listinfo/grassuser
>>
>
>

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

9

OK, I'll try again. Comments below:

Well, the example is a bit different:

http://grass.itc.it/gdp/html_grass63/v.dissolve.html
# remove duplicated tile boundaries:
v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl thresh=.01

Please note that you need tool=snap,break,rmdupl, otherwise it won't
work. Attributes should survive (they do for me in various maps).

I did try the full v.clean call the first time, and it hung part way
through processing (i.e. stopped responding) so I tried again with
only the rmdupl (incorrectly making the assumption that it was the
most important parameter for this task). I'll give it a try again now
with the full v.dissolve call, and wait it out.

I ran (v.clean imported out=cleaned tool=snap,break,rmdupl
thresh=0.01). The longest wait is while processing the "Break Lines
at Intersections" portion of the clean, which runs for ~20 mins on a
very small vector file, although this time it did complete
successfully.

> - at this point I noticed that the attribute values are not carried
> through and I'm left with only "id" and "cat" - why is this, and will
> it cause problems later on?

The problem originates from the incomplete v.clean call, I guess.

This is still an issue, even with the full v.clean call. When adding
the new "cleaned" vector to my project, I get the error "Warning:
Cannot select attributes from table 'cleaned'" Is this a GRASS/QGIS
integration problem? Is there another way to check if the attributes
are there, but not coming through?

# dissolve based on column attributes:
v.dissolve input=clc2000_clean output=clc2000_final col=CODE_00

Here's where I run into problems. I do not have a "col" that I wish
to dissolve on, rather I wish to do a "spatial" dissolve i.e. not
based on attributes. However, even if I did want to dissolve on
attributes, I would be unable to, as they do not come through the
clean process. Also, the help for v.dissolve in the version of GRASS
I'm using does not even list "col", as a parameter, rather it has only
'input', 'output' and 'layer.' Please advise as to the next steps.

Please try again and let us know where you found the misleading
documentation (so that we can fix it).

As I mentioned above, there is no misleading documentation, just my
incorrect assumption based on the CORINE example.

Thanks again or your help! It will be nice to have this figured out!

Cheers,

Darren

> On 5/28/07, Markus Neteler <neteler@itc.it> wrote:
> > Darren,
> >
> > could you be more specific about what you did (commands + flags/params),
> > which GRASS version etc? I just used this method recently again with
> > success.
> > The v.patch step in the CORINE example is necessary for *CORINE* since
> > you get vector tiles. If you have already a patched map, don't use it.
> >
> > Markus
> >
> > Darren Cope wrote on 05/28/2007 02:01 PM:
> > > Hi Markus,
> > >
> > > I must be missing something, because this still does not seem to work.
> > > I found another (non-GRASS) way to accomplish this, so the priority
> > > is not very high, but I'd still like to figure out the GRASS method.
> > > Is the v.patch step in the CORINE example necessary, or mostly just
> > > the v.clean step with rmdupl?
> > >
> > > Cheers,
> > >
> > > Darren
> > >
> > > On 5/16/07, Markus Neteler <neteler@itc.it> wrote:
> > >>
> > >> Hi Darren,
> > >>
> > >> I also stumbled over this problem, but we solved it. The trick is that
> > >> you first have to remove the duplicated tile boundaries, then dissolve
> > >> works.
> > >> See example for CORINE Landcover SHAPE files:
> > >> http://grass.itc.it/grass63/manuals/html63_user/v.dissolve.html
> > >>
> > >> Cheers
> > >> Markus
> > >>
> > >> Darren Cope wrote:
> > >> >
> > >> > Hi all,
> > >> >
> > >> > I'm new to GRASS, and using it in Windows via QGIS.
> > >> >
> > >> > I am attempting to do a "spatial dissolve" (i.e. not dissolve on an
> > >> > attribute, but rather just remove unnecessary tile boundaries) on a
> > >> > file that I've imported to GRASS from a shapefile, and am so far
> > >> > unsuccessful. The file contains waterbodies, and some of them are cut
> > >> > in pieces by tile boundaries. I would like to remove these
> > >> > boundaries. Can someone please help me out? I've tried combinations
> > >> > of v.extract -d with no success, and am not sure how the "category"
> > >> > value apply when I'm not dissolving on an attribute.
> > >> >
> > >> > So far my search of the archives has turned up something close, but
> > >> > nothing that seems to fit my situation exactly.
> > >> >
> > >> > Cheers,
> > >> >
> > >> > Darren Cope
> > >> > darrencope@gmail.com
> > >> > http://dmcope.freeshell.org
> >
> > ------------------
> > ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
> > ITC -> since 1 March 2007 Fondazione Bruno Kessler
> > ------------------
> >
> > _______________________________________________
> > grassuser mailing list
> > grassuser@grass.itc.it
> > http://grass.itc.it/mailman/listinfo/grassuser
> >
>
> --
> Darren Cope
> darrencope@gmail.com
> http://dmcope.freeshell.org
>
> _______________________________________________
> grassuser mailing list
> grassuser@grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser

_______________________________________________
grassuser mailing list
grassuser@grass.itc.it
http://grass.itc.it/mailman/listinfo/grassuser

--
Darren Cope
darrencope@gmail.com
http://dmcope.freeshell.org

10

On 5/29/07, Leonardo Lami <lami@faunalia.it> wrote:

> - run v.clean as per CORINE example (v.clean input=wateroriginal
> output=waterclean tool=rmdupl) in GRASS shell
> - at this point I noticed that the attribute values are not carried
> through and I'm left with only "id" and "cat" - why is this, and will
> it cause problems later on?
See the output message of v.in.ogr, maybe there is some problems in the
structure of the input table

Hi Leonardo:

Thanks for the idea. I had originally thought that the v.in.ogr was
fine, and that the attributes were lost in the v.clean step. However,
I looked again, and it does appear that only a portion of the
attributes (e.g. the first 137 features) came through during the
v.in.ogr step. That may potentially be the cause of the problems with
v.clean? I've attached the output of v.in.ogr, although I don't see
anything that indicated a problem?

---start output of v.in.ogr: ---

v.in.ogr 'dsn=C:/documents and
settings/dcope/desktop/shp/obm_OBMUSER_waterseg_polyne_poly.shp'
output=test -o
A datum name nad83 (North_American_Datum_1983) was specified without
transformation parameters.

Non-interactive mode: the GRASS default for nad83 is
towgs84=0.000,0.000,0.000.

Over-riding projection check.

Proceeding with import...

Layer: obm_OBMUSER_waterseg_polyne_poly

Importing map 1277 features...

-----------------------------------------------------

Building topology ...

Registering lines: 1000
1837 primitives registered

Building areas:

1530 areas built

1496 isles built

Attaching islands:

Attaching centroids:

Topology was built.

Number of nodes : 1663

Number of primitives: 1837

Number of points : 0

Number of lines : 0

Number of boundaries: 1837

Number of centroids : 0

Number of areas : 1530

Number of isles : 1496

Number of incorrect boundaries : 341

Number of areas without centroid : 1530

-----------------------------------------------------

Cleaning polygons, result is not guaranteed!
Building topology ...

Topology was built.

Number of nodes : 1663

Number of primitives: 1837

Number of points : 0

Number of lines : 0

Number of boundaries: 1837

Number of centroids : 0

Number of areas : -

Number of isles : -

-----------------------------------------------------

Break polygons:

Registering points ... 128830

All points (vertices): 144066

Registered points (unique coordinates): 128830

Points marked for break: 1947

Breaks: 0
Breaks: 13
Breaks: 22
Breaks: 38
Breaks: 41
Breaks: 68
<snip>
Breaks: 1279

-----------------------------------------------------

Remove duplicates:

Duplicates: 0
<snip>
Duplicates: 459

-----------------------------------------------------

Break boundaries:

Intersections: 0
Intersections: 0 (line 637)
Intersections: 0 (line 1243)
Intersections: 0 (line 1875)
Intersections: 0 (line 2119)
Intersections: 0 (line 2398)
Intersections: 0 (line 2623)
Intersections: 0 (line 2859)
Intersections: 0

-----------------------------------------------------

Remove duplicates:

Duplicates: 0

-----------------------------------------------------

Clean boundaries at nodes:

Modifications: 0
<snip>
Modifications: 0

-----------------------------------------------------

Change dangles to lines:

Removed dangles: 0 removed lines: 0

-----------------------------------------------------

Remove bridges:

Removed bridges: 0 removed lines: 0
<snip>
Removed bridges: 0 removed lines: 0

-----------------------------------------------------

Building topology ...

Building areas:

1712 areas built

1421 isles built

Attaching islands:

Topology was built.

Number of nodes : 1947

Number of primitives: 3116

Number of points : 0

Number of lines : 0

Number of boundaries: 3116

Number of centroids : 0

Number of areas : 1712

Number of isles : 1421

Number of areas without centroid : 1712

Layer: obm_OBMUSER_waterseg_polyne_poly

-----------------------------------------------------

-----------------------------------------------------

Building topology ...

Registering lines: 1000 2000 3000
3524 primitives registered

Building areas:

1712 areas built

1421 isles built

Attaching islands:

Attaching centroids:

Topology was built.

Number of nodes : 3233

Number of primitives: 3524

Number of points : 0

Number of lines : 0

Number of boundaries: 2238

Number of centroids : 1286

Number of areas : 1712

Number of isles : 1421

Number of areas without centroid : 426

-----------------------------------------------------

4 areas represent more (overlapping) features, because polygons
overlap in input layer(s). Such areas are linked to more than 1 row in
attribute table. The number of features for those areas is stored as
category in layer 2

1286 input polygons

total area: 1.945637e+008 (1712 areas)

overlapping area: 1.987796e+006 (4 areas)

area without category: 4.105847e+006 (426 areas)

Successfully finished

---end output of v.in.ogr: ---

11

I have probably the same problem as Darren.
I need to remove boundaries between adjacent maps, which were merged together (look at the picture http://best.krajinari.com/konfer.png). So I need to get only polygons boundaries in the map (attributes indeed). I tryed to use spatial dissolve (as described befor)
first : v.clean input=ostatni_plochy_extract output=plochy_clean type=line,boundary,area tool=break,rmdupl,snap tresh=.01
than : v.dissolve input=plochy_clean output=plochy_diss layer=1
But it doesn’t seems to make any changes.
Best regards
Martin