[GRASS-dev] v.edit

GRASS GIS GRASS GIS developer
1

Ok now v.edit's add functionality is completed. One can add point,line,area,boundary,centroid. Boundaries will not be given a cat.

Adding an area tries to put a centroid in the geographic mean, and if it fails it will exit, with nothing added.

if you give many co-ordinates when adding a point many points will be generated.

The cat support includes support for many cat's and ranges. This is for instance supported:
   v.edit map=test cat=267,347-350,353,356-359 coords=...
And if there are more points then given cats, the cat will just be increased by one. The example above will result in 10 cats:
267,347,348,349,350,353,356,357,358 and 359. If you give 11 point the eleventh point will get the next cat (which is 360)

--Wolf

--

<:3 )---- Wolf Bergenheim ----( 8:>

2

Hallo,

great work

On Tue, Jun 06, 2006 at 10:30:47AM +0300, Wolf Bergenheim wrote:

Ok now v.edit's add functionality is completed. One can add
point,line,area,boundary,centroid. Boundaries will not be given a cat.

Adding an area tries to put a centroid in the geographic mean, and if it
fails it will exit, with nothing added.

if you give many co-ordinates when adding a point many points will be
generated.

The cat support includes support for many cat's and ranges. This is for
instance supported:
  v.edit map=test cat=267,347-350,353,356-359 coords=...
And if there are more points then given cats, the cat will just be
increased by one. The example above will result in 10 cats:
267,347,348,349,350,353,356,357,358 and 359. If you give 11 point the
eleventh point will get the next cat (which is 360)

--Wolf

Why should a boundary NOT have category too? How would you distinguish
two different types of boundary arround one area? Example on

http://les-ejk.cz/tmp/boundaries.gif

One country (Sachsen) has 2 different types of boundaries (country and
state).

I thing, it is usefull to have a possibility for adding category number
(and attributes) to boundary too.

Or do I understand it wrong?

Jachym

--
Jachym Cepicky
e-mail: jachym.cepicky@centrum.cz
URL: http://les-ejk.cz
GPG: http://les-ejk.cz/gnupg_public_key/jachym_cepicky-gpg_public_key.asc
-----------------------------------------
OFFICE:
GDF-Hannover
Mengendamm 16d
30177 Hannover
Germany
e-mail: cepicky@gdf-hannover.de
URL: http://gdf-hannover.de
Tel.: +49 511-39088507

3

On Tue, 6 Jun 2006, Jachym Cepicky wrote:

Why should a boundary NOT have category too? How would you distinguish
two different types of boundary arround one area? Example on

At the moment because that is the way I coded, and I haven't seen a boundary with a cat yet. I can quite easily change it, if you think I should.

While we are talking about all this. Is there any such thing as an open boundary (a line of type GV_BOUNDARY that has different first and last points? As I understand it boundaries are lines that define the shape of an area and the centroid marks the "inside" of the area. So that way boundaries are not really part of the area, but rather marks its extents.

--W

--

<:3 )---- Wolf Bergenheim ----( 8:>

4

Jachym Cepicky wrote:

Why should a boundary NOT have category too? How would you distinguish
two different types of boundary arround one area? Example on

http://les-ejk.cz/tmp/boundaries.gif

One country (Sachsen) has 2 different types of boundaries (country and
state).

I thing, it is usefull to have a possibility for adding category
number (and attributes) to boundary too.

Or do I understand it wrong?

It can have its uses. You can give a boundary a cat with v.category if
you want.

In general it isn't needed, and worse can subtly change things (like
v.to.rast output) so should be used with caution.

v.edit could have the power to add boundary cats, just leave it out of
the GUI controls :wink:

Hamish

5

While we are talking about all this. Is there any such thing as an
open boundary (a line of type GV_BOUNDARY that has different first and
last points? As I understand it boundaries are lines that define the
shape of an area and the centroid marks the "inside" of the area. So
that way boundaries are not really part of the area, but rather marks
its extents.

Yes, try making one with the (old) v.digit. (red endpoints).

on exit:

Topology was built.
Number of nodes : 2
Number of primitives: 1
Number of points : 0
Number of lines : 0
Number of boundaries: 1
Number of centroids : 0
Number of areas : 0
Number of isles : 0
Number of incorrect boundaries : 1

Hamish

6

Hi,

On Tue, Jun 06, 2006 at 11:15:53PM +1200, Hamish wrote:

It can have its uses. You can give a boundary a cat with v.category if
you want.

In general it isn't needed, and worse can subtly change things (like
v.to.rast output) so should be used with caution.

v.edit could have the power to add boundary cats, just leave it out of
the GUI controls :wink:

Hamish

Did you see the last version of v.pydigit? Is that desired setting and behaviour ?

Jachym

--
Jachym Cepicky
e-mail: jachym.cepicky@centrum.cz
URL: http://les-ejk.cz
GPG: http://les-ejk.cz/gnupg_public_key/jachym_cepicky-gpg_public_key.asc
-----------------------------------------
OFFICE:
GDF-Hannover
Mengendamm 16d
30177 Hannover
Germany
e-mail: cepicky@gdf-hannover.de
URL: http://gdf-hannover.de
Tel.: +49 511-39088507

7

Wolf wrote:

Adding an area tries to put a centroid in the geographic mean, and if
it fails it will exit, with nothing added.

donut case? kidney shape ("C")?

Use Vect_get_point_in_area() to find a centroid that is really in the
area.

see v.category add GV_AREA.
[It tests for an existing one first with Vect_get_area_centroid()]

the vector lib has most common tools aready....

Hamish

8

Hamish wrote:

Wolf wrote:

Adding an area tries to put a centroid in the geographic mean, and if
it fails it will exit, with nothing added.

donut case? kidney shape ("C")?

Currently it will print an error message and exit. ):

Use Vect_get_point_in_area() to find a centroid that is really in the
area.

Thanks! I'll look in to it. (:

--W

--

<:3 )---- Wolf Bergenheim ----( 8:>

9

This sounds great.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

From: Wolf Bergenheim <wolf+grass@bergenheim.net>
Date: Tue, 6 Jun 2006 10:30:47 +0300 (EEST)
To: GRASS developers list <grass-dev@grass.itc.it>
Subject: [GRASS-dev] v.edit

Ok now v.edit's add functionality is completed. One can add
point,line,area,boundary,centroid. Boundaries will not be given a cat.

Adding an area tries to put a centroid in the geographic mean, and if it
fails it will exit, with nothing added.

if you give many co-ordinates when adding a point many points will be
generated.

The cat support includes support for many cat's and ranges. This is for
instance supported:
v.edit map=test cat=267,347-350,353,356-359 coords=...
And if there are more points then given cats, the cat will just be
increased by one. The example above will result in 10 cats:
267,347,348,349,350,353,356,357,358 and 359. If you give 11 point the
eleventh point will get the next cat (which is 360)

--Wolf

--

<:3 )---- Wolf Bergenheim ----( 8:>

10

Jachym,

See below

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

From: Jachym Cepicky <jachym.cepicky@centrum.cz>
Date: Tue, 6 Jun 2006 11:43:05 +0200
To: Wolf Bergenheim <wolf+grass@bergenheim.net>
Cc: GRASS developers list <grass-dev@grass.itc.it>
Subject: Re: [GRASS-dev] v.edit

Hallo,

great work

On Tue, Jun 06, 2006 at 10:30:47AM +0300, Wolf Bergenheim wrote:

Ok now v.edit's add functionality is completed. One can add
point,line,area,boundary,centroid. Boundaries will not be given a cat.

Adding an area tries to put a centroid in the geographic mean, and if it
fails it will exit, with nothing added.

if you give many co-ordinates when adding a point many points will be
generated.

The cat support includes support for many cat's and ranges. This is for
instance supported:
v.edit map=test cat=267,347-350,353,356-359 coords=...
And if there are more points then given cats, the cat will just be
increased by one. The example above will result in 10 cats:
267,347,348,349,350,353,356,357,358 and 359. If you give 11 point the
eleventh point will get the next cat (which is 360)

--Wolf

Why should a boundary NOT have category too? How would you distinguish
two different types of boundary arround one area? Example on

http://les-ejk.cz/tmp/boundaries.gif

One country (Sachsen) has 2 different types of boundaries (country and
state).

You can also think of this conceptually as 2 different areas (country and
state) that overlay. Or the area can simply have 2 attributes or even 2
layers (a state layer and a country layer). So there are a number of ways
to represent this situation.

As I said earlier, while it sometimes might be convenient for a boundary to
have a cat (with possibility of attributes) separate from that of an area, I
think it is better to make boundaries different from lines.

A line can be open or closed, has a cat and attributes. It is a vector
entity.

A boundary, while internally structured like a line, is part of a complex
entity called area. The complex area entity is composed of a closed line and
a point, and has a single cat for the closed line/point pair.

I think this kind of definition would make entity creation and management
easier than it is now. A boundary that is not part of an area and is not a
closed line is an odd, confusing entity IMHO. Could be convenient, I admit,
but I think that we are better off without it.

Michael

I thing, it is usefull to have a possibility for adding category number
(and attributes) to boundary too.

Or do I understand it wrong?

Jachym

--
Jachym Cepicky
e-mail: jachym.cepicky@centrum.cz
URL: http://les-ejk.cz
GPG: http://les-ejk.cz/gnupg_public_key/jachym_cepicky-gpg_public_key.asc
-----------------------------------------
OFFICE:
GDF-Hannover
Mengendamm 16d
30177 Hannover
Germany
e-mail: cepicky@gdf-hannover.de
URL: http://gdf-hannover.de
Tel.: +49 511-39088507

11

I agree with Michael. I think that we should strive to make the
topologic model as orthogonal as possible. More importantly, it should
be easy to understand and implement. Tools should enforce the model
not add to the confusion. One of the problems of operational GIS are
broken/unclean topology.

If we need more sophisticated topological entities than point, line,
area; then we should develop a higher-order topologic model that is
built out of the three primitive objects rather than hack the simple
model. For example, boundary lines for a single area with distinct
categories are merging the behavior of line entity with the area
entity. I think that is confusing.

On 6/6/06, Michael Barton <michael.barton@asu.edu> wrote:

Jachym,

See below

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

> From: Jachym Cepicky <jachym.cepicky@centrum.cz>
> Date: Tue, 6 Jun 2006 11:43:05 +0200
> To: Wolf Bergenheim <wolf+grass@bergenheim.net>
> Cc: GRASS developers list <grass-dev@grass.itc.it>
> Subject: Re: [GRASS-dev] v.edit
>
> Hallo,
>
> great work
>
> On Tue, Jun 06, 2006 at 10:30:47AM +0300, Wolf Bergenheim wrote:
>> Ok now v.edit's add functionality is completed. One can add
>> point,line,area,boundary,centroid. Boundaries will not be given a cat.
>>
>> Adding an area tries to put a centroid in the geographic mean, and if it
>> fails it will exit, with nothing added.
>>
>> if you give many co-ordinates when adding a point many points will be
>> generated.
>>
>> The cat support includes support for many cat's and ranges. This is for
>> instance supported:
>> v.edit map=test cat=267,347-350,353,356-359 coords=...
>> And if there are more points then given cats, the cat will just be
>> increased by one. The example above will result in 10 cats:
>> 267,347,348,349,350,353,356,357,358 and 359. If you give 11 point the
>> eleventh point will get the next cat (which is 360)
>>
>> --Wolf
>
> Why should a boundary NOT have category too? How would you distinguish
> two different types of boundary arround one area? Example on
>
> http://les-ejk.cz/tmp/boundaries.gif
>
> One country (Sachsen) has 2 different types of boundaries (country and
> state).

You can also think of this conceptually as 2 different areas (country and
state) that overlay. Or the area can simply have 2 attributes or even 2
layers (a state layer and a country layer). So there are a number of ways
to represent this situation.

As I said earlier, while it sometimes might be convenient for a boundary to
have a cat (with possibility of attributes) separate from that of an area, I
think it is better to make boundaries different from lines.

A line can be open or closed, has a cat and attributes. It is a vector
entity.

A boundary, while internally structured like a line, is part of a complex
entity called area. The complex area entity is composed of a closed line and
a point, and has a single cat for the closed line/point pair.

I think this kind of definition would make entity creation and management
easier than it is now. A boundary that is not part of an area and is not a
closed line is an odd, confusing entity IMHO. Could be convenient, I admit,
but I think that we are better off without it.

Michael
>
> I thing, it is usefull to have a possibility for adding category number
> (and attributes) to boundary too.
>
> Or do I understand it wrong?
>
> Jachym
>
> --
> Jachym Cepicky
> e-mail: jachym.cepicky@centrum.cz
> URL: http://les-ejk.cz
> GPG: http://les-ejk.cz/gnupg_public_key/jachym_cepicky-gpg_public_key.asc
> -----------------------------------------
> OFFICE:
> GDF-Hannover
> Mengendamm 16d
> 30177 Hannover
> Germany
> e-mail: cepicky@gdf-hannover.de
> URL: http://gdf-hannover.de
> Tel.: +49 511-39088507

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