[GRASS-user] r.convergence vs TCI (r.terraflow). Difference?

Dear community,
Can someone explain me the difference between r.convergence and the TCI calculated by r.terraflow.
Best regards
Rengifo Ortega


Von:grass-user-request@lists.osgeo.orggrass-user-request@lists.osgeo.org
An: grass-user@lists.osgeo.org
Gesendet: 21:00 Donnerstag, 31.März 2016
Betreff: grass-user Digest, Vol 119, Issue 61

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Today’s Topics:

  1. Output of i.segment (Jaya Krishnan)
  2. problem with g.proj.exe (Giuliano Urgeghe)
  3. Re: v.rast.stats with mode? (patrick s.)
  4. problem with g.proj.exe (Giuliano Urgeghe)
  5. Re: problem with g.proj.exe (Martin Landa)

Message: 1
Date: Wed, 30 Mar 2016 16:17:34 -0700
From: Jaya Krishnan <jayaakrish@gmail.com>
To: grass-user@lists.osgeo.org
Subject: [GRASS-user] Output of i.segment
Message-ID:
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Hi fellow GRASS users,

I have outputs of i.segment (object segmentation) for 30m Landsat imagery
from 4 dates. The segments are around 10000 each for each imagery. How can
I use these outputs for land cover change analysis? Do I have to vectorize
these and recode the classes, or is there a more efficient way?

Thanks!

Jaya
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Message: 2
Date: Thu, 31 Mar 2016 01:43:25 +0200
From: Giuliano Urgeghe <giuliano.u@gmail.com>
To: GRASS user list <grass-user@lists.osgeo.org>
Subject: [GRASS-user] problem with g.proj.exe
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Hi all,
today, I have a problem with my release "grass 6.4.4 with my sis " in
windows vista.
When I open my mapset, appears this error:
“g.proj.exe ha smesso di funzionare”.
Someone has an idea for a solution.
thanks in advance.
Giuliano
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Message: 3
Date: Thu, 31 Mar 2016 10:32:17 +0200
From: “patrick s.” <patrick_gis@gmx.net>
To: Anna Petrášová <kratochanna@gmail.com>
Cc: GRASS user list <grass-user@lists.osgeo.org>
Subject: Re: [GRASS-user] v.rast.stats with mode?
Message-ID: <56FCE091.2010203@gmx.net>
Content-Type: text/plain; charset=“utf-8”; Format=“flowed”

Following Anna’s suggestion I had to find out that r.mode has to option
to handle NULL values, i.e. exclude it from calculation? I need to
aggregate rasters to polygons, with rasters covering only a small part
of the polygon. As I realized now r.mode returns NULL in such case.
Setting NULL with r.null null=9999 it will return 9999 for all of these.

Is there a solution to that problem?
Patrick

On 16.03.2016 13:59, Anna Petrášová wrote:

On Wed, Mar 16, 2016 at 6:23 AM, patrick s. <patrick_gis@gmx.net
mailto:[patrick_gis@gmx.net](mailto:patrick_gis@gmx.net)> wrote:

Dear list

Is it possible to get the “mode” (most common occurring value) in
a polygon for discrete classes? It appears that v.rast.stats does
not have this option.

v.rast.stats uses r.univar and r.univar doesn’t have mode implemented
(it’s a TODO in manual). You can look at r.mode but it returns raster
map, not one number.

Anna

Thanks for a short feedback,
Patrick


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Message: 4
Date: Thu, 31 Mar 2016 15:36:38 +0200
From: Giuliano Urgeghe <giuliano.u@gmail.com>
To: GRASS user list <grass-user@lists.osgeo.org>
Subject: [GRASS-user] problem with g.proj.exe
Message-ID:
<CABQtJmRDj6bHEe34CpkwRuRmvx5Pqm8gf3P-8U59SFKwvdJBaw@mail.gmail.com>
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this ticket helped me!

has been fixed very well!

THANKS

https://trac.osgeo.org/grass/ticket/827
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Message: 5
Date: Thu, 31 Mar 2016 15:38:26 +0200
From: Martin Landa <landa.martin@gmail.com>
To: Giuliano Urgeghe <giuliano.u@gmail.com>
Cc: GRASS user list <grass-user@lists.osgeo.org>
Subject: Re: [GRASS-user] problem with g.proj.exe
Message-ID:
<CA+Ei1Oen8xEtdTqktrfGmiP_S811K=8EOd79yEzBR74iGvZG3g@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

Hi,

2016-03-31 15:36 GMT+02:00 Giuliano Urgeghe <giuliano.u@gmail.com>:

this ticket helped me!

has been fixed very well!

THANKS

https://trac.osgeo.org/grass/ticket/827

please consider to update your GRASS to version 7. Martin


Martin Landa
http://geo.fsv.cvut.cz/gwiki/Landa
http://gismentors.cz/mentors/landa


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End of grass-user Digest, Vol 119, Issue 61


Dear community,
Can someone explain me the difference between r.convergence and the TCI

calculated by r.terraflow.

from the manuals:

https://grass.osgeo.org/grass71/manuals/r.terraflow.html

r.terraflow also computes the tci raster (topographic convergence index,
defined as the logarithm of the ratio of flow accumulation and local slope).

https://grass.osgeo.org/grass70/manuals/addons/r.convergence.html

Convergence index is a terrain parameter which show the structure od the
relief as a set of convergent areas (channels) and divergent areas (ridges).

AFAIU r.convergence calculates kind of geomorphological items (convergent
areas (channels) and divergent areas (ridges)); r.terraflow's tci indicates
terrain derivatives (ratio of flow accumulation and local slope).

-----
best regards
Helmut
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