[GRASS-dev] Need ideas for a masters thesis...

Helena Mitasova hmitaso at unity.ncsu.edu
Wed Nov 18 00:23:17 EST 2009


can you add those scripts with links to the Wiki add ons?

those are very useful modules and they could save some people time re- 
what has already been done,

thank you,


Helena Mitasova
Associate Professor
Department of Marine, Earth
and Atmospheric Sciences
1125 Jordan Hall, Campus Box 8208
North Carolina State University
Raleigh NC 27695-8208

On Nov 16, 2009, at 5:07 AM, vetter michael wrote:

> We already did  a method to derive river centerlines based on  
> r.thin and a method to calculate cross sections (see the scripts).  
> It is not a method to derive the flow line of the river, but you  
> can calculate the center line of the river.
> For those you need a very precise water surface polygon. To derive  
> such a high quality water surface you need a ortho image or a good  
> DTM like a 1m LiDAR DTM. By doing a classification using region  
> growing of height differences and the slope.
> you can check out the scripts here:
> centerline:        http://www.uibk.ac.at/geographie/personal/vetter/ 
> scripts/v.centerline.sh
> smoothline:      http://www.uibk.ac.at/geographie/personal/vetter/ 
> scripts/v.smooth.tar
> crossprofile:    http://www.uibk.ac.at/geographie/personal/vetter/ 
> scripts/v.crossprofile.tar
> The sand or gravel banks are really a big problem in deriving a  
> water surface. Such a solution is presented in:
> Höfle, B., Vetter**, M., Pfeifer, N., Mandlburger, G., Stötter, J. * 
> (2009)*: Water surface mapping from airborne laser scanning using  
> signal amplitude and elevation data. Earth Surface Processes and  
> Landforms, p. 1635-1649. DOI:10.1002/esp.1853.
>     good luck,
> Michael
>> Thomas wrote:
>>> If you come from a hydraulics background… one very
>>> important need is the ability to generate channel
>>> cross-sections interactively for, say, HEC-RAS and then do
>>> flood inundation mapping from HEC-RAS from the modeling
>>> results — I would think this would be a huge
>>> contribution.
>> to get a good cross section you need to set it perpendicular to  
>> the river's
>> center line. Which means you need a good river centerline. Which  
>> means you
>> have to deal with the "river mile problem".
>> raster tools are not always good here as the river can be very thin
>> compared to the overall length leading to untenable resolution  
>> settings
>> to get an good result. (r.cost + r.param.scale to pull out the cost
>> ridges or r.slope.aspect to pull out the maxima from the 1st  
>> derivative
>> of the cost works, but the resolution issue gets ya)
>> any thoughts? some sort of reverse v.buffer?
>> small islands within the river also cause havoc with many  
>> computational
>> approaches.
>> Hamish
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