Hello GrassGurus:
We have been working for more than 3 years with GRASS. Until we have used it
as a graphic database with plotting aim and simple analysis of overlay
operations, proximity functions, spread functions and seek functions.
Lately we have developed some models with the combination of the map algebra
and unix scripts.
In this line of progressive complication we have gone into the network
problematic (transport of water through a system of irrigation channels,
ordering of a river network, etc) and its resolution in GRASS environment.
That's my question: How is treated the problems that implicate networking in
GRASS? Have they to be solved only by means of combination of r.mapcalc
instruccions in UNIX scripts loops? Have they to accomplish any intermediate
step? Do the misterious, for me, cost maps and this asociate functions play
any role in this point? And, would the run times of the network functions
allow real time applications?
As a first example of this problematic and other similars, here you are a
case:
We desire to improve the quality of our DEMs by means of incorporating
complementary information to the contour lines, in the sites file to
interpolate. This new information is of points type (3d vertex points) and
linear type (stream networks, ridges, etc), which have been digitized from the
same maps as the contour lines. We want that this linear information
to be reflected in the created DEMs. The trouble is that vectorial
information is 2D, it hasn't elevation. Here begin the problem:
The stream and contour line vector maps are converted to raster.
From this maps, by means of the map algebra (r.mapcalc), we create a new map,
in which all the cells of the stream map that have a value different of 0 in
the contour map take this value in the new map. Now we have a result map
which have the elevation in the intersection of the streams with the contour
lines. Later we have to fill in with elevation values the stream path in all
its length. For this, in all the stream cells, we have to follow its path in
the two senses, until the two nearest cells which have elevation value are
found. The elevation value of the target cell is equal to the lineal
interpolation along the river path of this two nearest cells with elevation
value. The problem is how to find from a stream cell the two nearest cell
with elevation value following the stream path in both senses. Could it
be made with neighbouring loops? With networks functions?
Thanks in advance.
Evaristo.
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__ __
/ / Evaristo QUIROGA RAIMUNDEZ / /
___/ / ___/ /
/ / / /
/ / UNIVERSIDAD AUTONOMA DE BARCELONA / /
\__/\\ Gabinete de Analisis Territorial y Ambiental \__/\\
\\__ Unidad de Geodinamica Externa y Hidrogeologia \\__
/ /\ Edificio CS / /\
\ / /\ 08193 - Bellaterra (BARCELONA) \ / /\
\ / \ SPAIN - EU \ / \
\___/ email: evaristo@cataw.uab.es \___/
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