Advice wanted!
As a Grass-novice, doing my first real GIS project, I would like to ask the more
experienced users for some comments about the following problem.>From a set of digitized contourlines (converted from ARC-INFO format), I want to
make an elevation model for a river basin in Austria. My contourlines represents
elevation, with 200m intervals. The river basin is situated within a region of
183 X 148 km2 (=DEFAULT REGION), and my plan is to use a resolution of 100m in
both the x- and y- directions (possibly 50m). Later the elevation model is going
to be used for hydrological analyses.I believe that the process of generating the elevation model will consist of the
steps: 1) converting the vectorlines to rasterlayers of lines or sites, and 2)
running a surface interpolation program. Before starting I would be very glad to
hear some comments about the following questions.1)
When using the v.to.rast / v.to.sites programs:
Will a resolution of 100x100m be appropriate to get a useful result when I
convert the vector-format contourlines into raster-format layers of lines or
sites (I guess the landscape here in Austria may be considered rather hilly).
Well, you might consider two factors here: the scale of your original
elevation model and the size of your resulting files. If your
contourline map is at 1:200 000 then it probably isn't worth the trouble
trying a 50x50 m resolution. And as you point out at 3., your file will
relatively large even at 100x100 m.
2)
Which of the programs r.surf.contour, r.surf.idw, r.surf.idw2, s.surf.idw,
s.surf.tps or others is best for this task?
Nothing is 'best', but the idw methods are conceptually a lot simpler.
r.surf.contour usually gives the visually most appealing result with
contour lines, whereas the result of s.surf.tps largely depends on your
choice of the input parameters and type of data.
3)
183 x 148 km2 and a resolution of 100 m means 1830 x 1480 = 2 708 400 raster
cells. Can I expect my HP7000 to complete such a task within a day? ..week?
..month? ..year?Any good advice or comments, experiences would be highly appreciated!
Trond Rinde
Good luck!
Philip Verhagen
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