[GRASS-user] Problem with r.watershed in Spearfish

GRASS GRASS user
1

Hi list!

I often used r.watershed without problems, but today i had a very strange one. Please can anyone verify that?
I used Spearfish mapset, map: elevation.10m:

g.region res=100
r.watershed elevation=elevation.10m@PERMANENT threshold=100 accumulation=acc_10 drainage=dir_10 stream=str_10 convergence=5 memory=300

The stream map has many streams with 0 value.
The problem is only with res=100.
Does r.watershed fail?

Thank you

--
Eng. Margherita Di Leo
Ph.D. Candidate
Methods and Technologies for Environmental Monitoring
Department of Environmental Engineering and Physics (DIFA)

University of Basilicata Campus Macchia Romana
85100 - Potenza Italy

Office: +39-0971205363
Fax: +39-0971205160

2

Margherita,

Check with g.region -p and see how many 100x100 pixels you have.
May be it is very small for your threshold.

best

milton

2010/1/25 Margherita Di Leo <diregola@gmail.com>

Hi list!

I often used r.watershed without problems, but today i had a very strange one. Please can anyone verify that?
I used Spearfish mapset, map: elevation.10m:

g.region res=100
r.watershed elevation=elevation.10m@PERMANENT threshold=100 accumulation=acc_10 drainage=dir_10 stream=str_10 convergence=5 memory=300

The stream map has many streams with 0 value.
The problem is only with res=100.
Does r.watershed fail?

Thank you

–
Eng. Margherita Di Leo
Ph.D. Candidate
Methods and Technologies for Environmental Monitoring
Department of Environmental Engineering and Physics (DIFA)

University of Basilicata Campus Macchia Romana
85100 - Potenza Italy

Office: +39-0971205363
Fax: +39-0971205160

grass-user mailing list
grass-user@lists.osgeo.org
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3

Hi Milton,

Thank you for answering.

Milton Cezar Ribeiro wrote:

Margherita,
Check with g.region -p and see how many 100x100 pixels you have.

GRASS 6.5.svn (spearfish60):~ > g.region -p
projection: 1 (UTM)
zone: 13
datum: nad27
ellipsoid: clark66
north: 4928000
south: 4914000
west: 590000
east: 609000
nsres: 100
ewres: 100
rows: 140
cols: 190
cells: 26600

May be it is very small for your threshold.

I don't think so, because the streams are well delineated. The problem is the value assigned to them (zero).

Cheers

best
milton
2010/1/25 Margherita Di Leo <diregola@gmail.com <mailto:diregola@gmail.com>>

    Hi list!

    I often used r.watershed without problems, but today i had a very
    strange one. Please can anyone verify that?
    I used Spearfish mapset, map: elevation.10m:

    g.region res=100
    r.watershed elevation=elevation.10m@PERMANENT threshold=100
    accumulation=acc_10 drainage=dir_10 stream=str_10 convergence=5
    memory=300

    The stream map has many streams with 0 value.
    The problem is only with res=100.
    Does r.watershed fail?

    Thank you

Eng. Margherita Di Leo
Ph.D. Candidate
Methods and Technologies for Environmental Monitoring
Department of Environmental Engineering and Physics (DIFA)

University of Basilicata Campus Macchia Romana
85100 - Potenza Italy

Office: +39-0971205363
Fax: +39-0971205160

4

Margherita Di Leo pisze:

Hi list!

I often used r.watershed without problems, but today i had a very strange one. Please can anyone verify that?
I used Spearfish mapset, map: elevation.10m:

g.region res=100
r.watershed elevation=elevation.10m@PERMANENT threshold=100 accumulation=acc_10 drainage=dir_10 stream=str_10 convergence=5 memory=300

The stream map has many streams with 0 value.
The problem is only with res=100.
Does r.watershed fail?

Thank you

confirmed for resolution between 90 to 110. With less than 90 and over 110 everythink is OK
J.

5

Fixed in all branches r40656-9

Markus M

Jaros?aw Jasiewicz wrote:

Margherita Di Leo pisze:

Hi list!

I often used r.watershed without problems, but today i had a very strange one. Please can anyone verify that?
I used Spearfish mapset, map: elevation.10m:

g.region res=100
r.watershed elevation=elevation.10m@PERMANENT threshold=100 accumulation=acc_10 drainage=dir_10 stream=str_10 convergence=5 memory=300

The stream map has many streams with 0 value.
The problem is only with res=100.
Does r.watershed fail?

Thank you

confirmed for resolution between 90 to 110. With less than 90 and over 110 everythink is OK
J.
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