[GRASS-dev] v.clean threshold value unit for 'prune'

GRASS GRASS developer
1

Hi

I am using the v.clean tool with the option "prune". According to the manual, threshold values have to be in map units. I am using this with a latlon map with vertices as close as 0.0001 degrees. However, v.clean only removes vertices at threshold values of about 50 or up. This seems to suggest that the tools assumes threshold values are in meters?

Best wishes,

Paulo

2

On Thu, Jan 26, 2017 at 10:51 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

Hi

I am using the v.clean tool with the option “prune”. According to the manual, threshold values have to be in map units. I am using this with a latlon map with vertices as close as 0.0001 degrees. However, v.clean only removes vertices at threshold values of about 50 or up. This seems to suggest that the tools assumes threshold values are in meters?

The prune tool of v.clean never really worked. Please use v.generalize instead.

Markus M

Best wishes,

Paulo

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3

OK, will do. Still the question remains whether this is a bug, an error in the manual page (i.e., threshold values are not in mapping units, but in meters like for the rmarea) , or I am doing something wrong (note that it seems to work fine if one assumed threshold values have to be in meters). If a bug or error in the manual page, I can create a ticket.

···

On 26-01-17 11:03, Markus Metz wrote:

On Thu, Jan 26, 2017 at 10:51 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

Hi

I am using the v.clean tool with the option “prune”. According to the manual, threshold values have to be in map units. I am using this with a latlon map with vertices as close as 0.0001 degrees. However, v.clean only removes vertices at threshold values of about 50 or up. This seems to suggest that the tools assumes threshold values are in meters?

The prune tool of v.clean never really worked. Please use v.generalize instead.

Markus M

Best wishes,

Paulo

grass-dev mailing list
grass-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-dev

4

On Thu, Jan 26, 2017 at 11:15 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

On 26-01-17 11:03, Markus Metz wrote:

On Thu, Jan 26, 2017 at 10:51 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

Hi

I am using the v.clean tool with the option “prune”. According to the manual, threshold values have to be in map units. I am using this with a latlon map with vertices as close as 0.0001 degrees. However, v.clean only removes vertices at threshold values of about 50 or up. This seems to suggest that the tools assumes threshold values are in meters?

The prune tool of v.clean never really worked. Please use v.generalize instead.

OK, will do. Still the question remains whether this is a bug, an error in the manual page (i.e., threshold values are not in mapping units, but in meters like for the rmarea) , or I am doing something wrong (note that it seems to work fine if one assumed threshold values have to be in meters). If a bug or error in the manual page, I can create a ticket.

It’s a bug in the code [0], the algorithm is not working properly. There is v.generalize, therefore I recommend to remove the prune tool from v.clean.

Markus M

[0] https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/diglib/prune.c

Markus M

Best wishes,

Paulo

grass-dev mailing list
grass-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-dev

5

+1 if it doesn’t work properly and it is a won’t fix better to remove

···

On 26-01-17 14:38, Markus Metz wrote:

On Thu, Jan 26, 2017 at 11:15 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

On 26-01-17 11:03, Markus Metz wrote:

On Thu, Jan 26, 2017 at 10:51 AM, Paulo van Breugel <p.vanbreugel@gmail.com> wrote:

Hi

I am using the v.clean tool with the option “prune”. According to the manual, threshold values have to be in map units. I am using this with a latlon map with vertices as close as 0.0001 degrees. However, v.clean only removes vertices at threshold values of about 50 or up. This seems to suggest that the tools assumes threshold values are in meters?

The prune tool of v.clean never really worked. Please use v.generalize instead.

OK, will do. Still the question remains whether this is a bug, an error in the manual page (i.e., threshold values are not in mapping units, but in meters like for the rmarea) , or I am doing something wrong (note that it seems to work fine if one assumed threshold values have to be in meters). If a bug or error in the manual page, I can create a ticket.

It’s a bug in the code [0], the algorithm is not working properly. There is v.generalize, therefore I recommend to remove the prune tool from v.clean.

Markus M

[0] https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/diglib/prune.c

Markus M

Best wishes,

Paulo

grass-dev mailing list
grass-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-dev

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6

On Thu, Jan 26, 2017 at 2:38 PM, Markus Metz
<markus.metz.giswork@gmail.com> wrote:
...

It's a bug in the code [0], the algorithm is not working properly. There is
v.generalize, therefore I recommend to remove the prune tool from v.clean.

Maybe keep (for consistency) and replace the functionality with an
G_fatal_error() pointing the user to v.generalize?

markusN

Markus M

[0]
https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/diglib/prune.c

7

On 26 January 2017 11:53:30 pm Markus Neteler <neteler@osgeo.org> wrote:

On Thu, Jan 26, 2017 at 2:38 PM, Markus Metz
<markus.metz.giswork@gmail.com> wrote:
…

It’s a bug in the code [0], the algorithm is not working properly. There is
v.generalize, therefore I recommend to remove the prune tool from v.clean.

Maybe keep (for consistency) and replace the functionality with an
G_fatal_error() pointing the user to v.generalize?

For the GUI, and the manual page, I think it would be better if the functionality is removed completely. Presenting an option that is really not available would, i.m.h.o. be confusing.

For command line use, it is good to get a error with pointer to v.generalize if users attempt to use ‘prune’ in v.clean. Especially important to warn people properly if using this in a script.

For legacy reasons, it is furthermore probably good to mention in the Note section of the help file that this function has been removed and that the user can use v.generalize for this.

Just my 2ct.

markusN

Markus M

[0]
https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/diglib/prune.c

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Excuse my brevity