[GRASS-user] derive points outlet from r.stream.extract

Giuseppe_Amatulli · April 23, 2020, 6:53pm

Hi,
I’m trying to extract the outlet location from the
r.stream.extract stream_vector=stream attribute.

In particular the manual for r.stream.extract reports:

“In layer 2, categories are identical to type_code in layer 1 with additional category 2 = outlet for outlet points.”

I want to be able to extract only the points of layer 2 where category = 2.

However when I run

v.db.connect -p map=stream
Vector map is connected by:
layer <1/stream> table in database </tmp/grass7-ga254-12721/tmploc/PERMANENT/sqlite/sqlite.db> through driver with key

I can see only layer 1 (which does not contain category 2).

Is there a way to connect to layer 2?
How I can be sure that also layer 2 has been created and is not missing?
Thanks

Giuseppe

GRASS 7.6.0 (tmploc):/gpfs/scratch60/fas/sbsc/ga254/dataproces/MERIT_HYDRO > v.info map=stream

···

Giuseppe Amatulli, Ph.D.

Research scientist at
School of Forestry & Environmental Studies
Center for Research Computing
Yale University
New Haven, CT, USA
06511

Teaching: http://spatial-ecology.net
Work: https://environment.yale.edu/profile/giuseppe-amatulli/

neteler · April 27, 2020, 10:25am

Hi Giuseppe,

Could you post a reproducible example with North Carolina samle data?
(being tight on time it would help)

Best
Markus

On Thu, Apr 23, 2020 at 8:53 PM Giuseppe Amatulli
<giuseppe.amatulli@gmail.com> wrote:

Hi,
I'm trying to extract the outlet location from the
r.stream.extract stream_vector=stream attribute.
In particular the manual for r.stream.extract reports:

"In layer 2, categories are identical to type_code in layer 1 with additional category 2 = outlet for outlet points."

I want to be able to extract only the points of layer 2 where category = 2.
However when I run

v.db.connect -p map=stream
Vector map <stream> is connected by:
layer <1/stream> table <stream> in database </tmp/grass7-ga254-12721/tmploc/PERMANENT/sqlite/sqlite.db> through driver <sqlite> with key <cat>

I can see only layer 1 (which does not contain category 2).

Is there a way to connect to layer 2?
How I can be sure that also layer 2 has been created and is not missing?
Thanks
Giuseppe

GRASS 7.6.0 (tmploc):/gpfs/scratch60/fas/sbsc/ga254/dataproces/MERIT_HYDRO > v.info map=stream
+----------------------------------------------------------------------------+
| Name: stream |
| Mapset: PERMANENT |
| Location: tmploc |
| Database: /tmp/grass7-ga254-25033 |
| Title: |
| Map scale: 1:1 |
| Name of creator: ga254 |
| Organization: |
| Source date: Thu Apr 23 14:42:51 2020 |
| Timestamp (first layer): none |
|----------------------------------------------------------------------------|
| Map format: native |
|----------------------------------------------------------------------------|
| Type of map: vector (level: 2) |
| |
| Number of points: 250905 Number of centroids: 0 |
| Number of lines: 245570 Number of boundaries: 0 |
| Number of areas: 0 Number of islands: 0 |
| |
| Map is 3D: No |
| Number of dblinks: 1 |
| |
| Projection: Latitude-Longitude |
| |
| N: 77:06:40.5N S: 73:10:55.5N |
| E: 158:07:46.5E W: 135:26:34.5E |
| |
| Digitization threshold: 0 |
| Comment: |
| |
+----------------------------------------------------------------------------+

--
Giuseppe Amatulli, Ph.D.

Research scientist at
School of Forestry & Environmental Studies
Center for Research Computing
Yale University
New Haven, CT, USA
06511
Teaching: http://spatial-ecology.net
Work: https://environment.yale.edu/profile/giuseppe-amatulli/
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user

--
Markus Neteler, PhD
https://www.mundialis.de - free data with free software
https://grass.osgeo.org
https://courses.neteler.org/blog

hcho · April 29, 2020, 11:18pm

Giuseppe,

r.stream.extract does not link a table to layer 2, but layer 2 is there. You can display outlets in GUI. Select layer=2 and cat=2 in d.vect.

Now, you want to extract the outlets.

v.extract input=extract_output layer=2 cat=2 output=outlets1

The outlets are still in layer 2 in the outlets1 map and they all have the same cat (2).

v.category map=outlets1 option=report

Change the layer from 2 to 1.
v.category input=outlets1 layer=2,1 option=chlayer output=outlets2

Delete all cats (2) because they’re just the same.(useless).
v.category input=outlets2 option=del cat=-1 output=outlets3

Add unique cats.
v.category input=outlets3 option=add output=final_outlets

Let’s see.
v.report map=final_outlets option=coor

How do you link these points in final_outlets back to the original extract_output? Now, you need to add a table to final_outlets.
v.db.addtable map=final_outlets column=‘src_cat int’

v.what.vect map=final_outlets col=src_cat query_map=extract_output query_column=cat

Check

v.report map=final_outlets option=coor

Hope this helps.

Best,
Huidae

···

Huidae Cho, Ph.D., GISP
GRASS GIS Developer
https://idea.isnew.info

Giuseppe_Amatulli · April 30, 2020, 12:11am

Thanks Huidae (& Markus),
I was writing to the list when I get your message.
In the end, I discover that the outlet are visible by v.category
v.category input=stream layer=2 type=point option=print
and I was able to directly convert to raster by
v.to.rast input=stream type=point use=cat label_column=type_code output=outlet cats=2

Probably is good to insert in the manual that the layer=2 is visible with v.category.

Thanks again
Giuseppe
p.s. I will write another message concerning some border effect in r.stream.basins

(attachments)

···

Giuseppe Amatulli, Ph.D.

Research scientist at
School of Forestry & Environmental Studies
Center for Research Computing
Yale University
New Haven, CT, USA
06511

Teaching: http://spatial-ecology.net
Work: https://environment.yale.edu/profile/giuseppe-amatulli/