[GRASS-user] grass-user Digest, Vol 103, Issue 47

Michael Barton Michael.Barton at asu.edu
Sat Nov 29 20:51:04 PST 2014


r.stream.extract can make the raster streams—ones that are pretty much equivalent to those made with r.watershed. But it can’t do stream profiles AFAICT. Also, like r.watershed, it extracts a stream network, not a particular stream. That is why we’re using r.drain to extract a particular drainage.

MICHAEL
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice:  480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu



On Nov 29, 2014, at 4:40 PM, grass-user-request at lists.osgeo.org<mailto:grass-user-request at lists.osgeo.org> wrote:

Re: [GRASS-user] how to change all cats in a vector line


Michael Barton wrote
Hi Markus,

What I'm trying to do is start with a raster stream map from r.drain and
convert it to a sequence of vector points, where each point has
information as to its position along the stream. I then use the points for
sampling a stream profile and related information. Oddly enough, with all
of the very useful stream analysis modules, there is nothing I could find
to generate the data for a stream profile (distance from outlet or from
headwaters vs. elevation).

v.to.points does a nice job of creating a sequence of evenly spaced points
with information about their location along a line (the "along" field).
BUT, if the line is composed of multiple segments or even if it has an
irregularity in it, the "along" values start over again from 0. The only
way I can use it is if I have a very clean and continuous vector line with
only a single cat.

This has proven surprisingly difficult to obtain reliably from my raster
stream map. So far, the only way has been to do a two sequences of v.clean
(with thresholds 1.5 X the raster resolution) and v.build.polylines. If
you have any better suggestion, I'd love to hear it.

Thanks again for the polylines idea. That was a big help.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice:  480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu<http://csdc.asu.edu/>




On Nov 29, 2014, at 10:20 AM, Michael Barton <

Michael.Barton@

> wrote:

Thanks. This helped.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Head, Graduate Faculty in Complex Adaptive Systems Science
Arizona State University

voice:  480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC)
fax: 480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu<http://csdc.asu.edu/>















On Nov 29, 2014, at 1:23 AM, Markus Neteler <

neteler@

> wrote:

On Sat, Nov 29, 2014 at 6:16 AM, Michael Barton <

Michael.Barton@

> wrote:
I have a vector line that is divided into 12 cat values. I’d like all
of the
line to have a single cat value. I’ve tried v.category to no avail. If
I
delete all categories and then add new categories, I get 12 cats again.
And
I can find no other way to get a single cat for the entire line.
Hopefully
someone can tell what I’m missing here.

Please try to use
http://grass.osgeo.org/grass70/manuals/v.build.polylines.html

Markus


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-----
best regards
Helmut

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