[GRASS-dev] Re: [GRASS GIS] #1577: r.stream.extract/r.stream.order - "calculated" mainchannel vs. "real" mainchannel

[Helmut Kudrnovsky]

Hi,

Jarek:
>> the mentionned "real" mainchannel is the part of real Austrian river
>> network
>> (i.e. listed in the annual Austrian hydrographical handbook as the river
>> 'Isel')
>It is popular argument against algorithmic approach. Usually computer
>algorithms cannot reproduce arbitrary human decisions :-( 

Markus M:

>As Jarek said, there is nothing like the one and only "real"
>mainchannel because there a different definitions on how to determine
>the main channel. You would need to get the definition of "real
>mainchannel" out of the Austrian hydrographical handbook,

in this example it's based on hydrographical characteristics:

- the "real" mainchannel (river Isel) has an (nival)/gacial runoff regime
- the calculated mainchannel (river Schwarzach) has an nival runoff regime,
and flows into the river Isel

Jarek, Markus M, thanks a lot for the insight!

best regards
Helmut

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best regards
Helmut
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