I do this by getting the Strahler stream order for all stream
reaches (using the GRASS r.stream.order addon). Then I display the
streams with line width determined by the stream order. Looks pretty
nice :-)
<shameless plug>
http://www.surfaces.co.il/strahler-stream-order-in-grass/
</shameless plug>
On 07/14/2015 11:08 PM, Luca Galuppini
wrote:
Dear all
i have this idea of rendering a river network so
that each river starts as a very thin blue line, and
the line width increases little by little as the
river goes.
i wouldn't like to modify the original file (eg
cutting rivers in pieces and give a different width to
each piece) but all rivers are digitized with the
right direction so i was wondering if there is an
_expression_ to teach qgis what is the start end of a
river, and assign a wider line for any given distance,
for example:
from start to 200m - line width 0.1
from 200m to 400m - line width 0.2
from 400m and over - line width 0.3
i think this is an interesting problem because i cannot find a
"from - to" command in qgis _expression_ language, neither i
know how to properly exploit the line direction with code,
which would come useful in many other ways...
any python expert out there can help?
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