[GRASS-user] Different distances to outlet for r.stream.order and r.stream.distance

[Markus Metz]

On Wed, Sep 21, 2016 at 1:26 PM, Mira Kattwinkel
<kattwinkel-mira at 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-mira at 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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>>> grass-user mailing list
>>> grass-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/grass-user
>
>
> --
> Dr. Mira Kattwinkel
> Quantitative Landscape Ecology
> Institute for Environmental Sciences
> University of Koblenz-Landau
> Fortstraße 7
> 76829 Landau
> Germany
> Fon: + 49 6341 280-31553
>