Dear Markus, dear List

It is much better now but still not exactly the same. Close to the outlet, the difference in distance to the outlet is about 30 cm (Fig_1b) and in the middle of the network it's about 80 cm (Fig_2b). The upDist raster produced with r.stream.distance gives the exact length I would expect (for Fig_1b: 6 * sqrt(2 * 25.0235 ^2) = 212.33) while r.stream.order still results in slightly to high values. .


That's good enough for the task I am working on but I wonder why this is the case.

Btw, I checked and my dem really has a cell size of 25.0235. I do not know why this is the case.

Cheers,

Mira


On 21/09/16 14:33, Markus Metz wrote:
On Wed, Sep 21, 2016 at 1:26 PM, Mira Kattwinkel
<kattwinkel-m...@uni-landau.de>  wrote:
Thanks a lot!

I saw that you uploaded a revision. Can you please give me a hint how I
upgrade to the revised version of r.stream.order? I am running Linux Mint
17.3 and Windows 7.

I have fixed another bug in r.stream.order (r69543): the stream
segment lengths are now identical to the lengths of the vector lines
and the out_dist value of r.stream.order matches now the output of
r.stream.distance. BTW, any reason why the resolution is 25.023 and
not exactly 25?

Markus M

I found that there are nightly pre-built Addon executables for Windows, so I
will try that tomorrow. What about Linux? Is it sufficient to just reinstall
the addon?


All the best,

Mira



Am 21.09.2016 um 11:08 schrieb Markus Metz:
On Tue, Sep 20, 2016 at 10:53 AM, Mira Kattwinkel
<kattwinkel-m...@uni-landau.de>  wrote:
Dear List

r.stream.order gives, among other output, the distance of current the
stream
init from the outlet of the catchment ('out_dist'). So for the most
downstream segment this is identical to the length of the segment.
r.stream.distance calculates the distance to the outlet and results in a
raster file. Both are based on a stream raster and a direction raster.

When I compare the results, they are slightly different, although based
on
the same input files (see the attached Fig1). The raster value is 212.33
at
the junction, while the out_dist of the line is 237.69. The difference is
one cellsize (25.023 in may example), probably due to the horizontal bit
of
the line at the end (upper right of the figure).
Yes, this horizontal bit of the line is a bug in r.stream.order, the
stream vector is leaving the current region or going into a NULL cell.
All other r.stream.* modules place the outlet on a valid cell. Fixed
in r69542.

However, this difference is
not fixed. In the middle of the network (Fig2) it is larger (81028.9 -
81002.89 = 27).
What is the difference in the middle of the network now with r69542?

Markus M

What is the reason for this difference? Is this a bug or a wanted
behaviour?

I want to extract the position of points on the network (i.e. upstream of
a
junction on the lines). To this end, I planned to use the upstream
distance
of the points and the out_dist of the segments (length(segment) -
(out_dist(segment) - upDist(point)) = position(point)).
Has anybody another idea how to accomplish this?

Thanks a lot,
Mira


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Dr. Mira Kattwinkel
Quantitative Landscape Ecology
Institute for Environmental Sciences
University of Koblenz-Landau
Fortstra├če 7
76829 Landau
Germany
Fon: + 49 6341 280-31553


--
Dr. Mira Kattwinkel
Quantitative Landscape Ecology
Institute for Environmental Sciences
University of Koblenz-Landau
Fortstra├če 7
76829 Landau
Germany
Phone: + 49 6341 280-31553
Office: Building I, Room 2.02

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