[Gvsig_english] DEM generating

[Antonio Falciano]

Antonio Falciano ha scritto:
> Dietrich Schröder ha scritto:
>> Yes, the workflow will give some results. I've used this workflow to
>> create a DEM. Unfortunately, the DEM will be not of high quality, as the
>> "steps" due to the line structure can clearly be seen in the DEM.
> 
> Sincerely speaking, I don't like this approach because it's so much
> deterministic and "Void filling" tool is too much slower to interpolate
> several No Data values, especially when cell size is high and/or raster
> extent is big. It seems like a proof of concept.
> An alternative way consists into conversion of contour lines into points
> by "Line to equispaced points" tool and the application of an
> interpolation method (e.g. IDW). Finally, if the result raster has some
> No Data values (only in this case!), we can use "Void filling" tool.

Hi all,
let me clarify my previous remarks because I have said some rubbish.
I have discovered that the latest stable release of Sextante (0.3)
contains useful informations about its algorithms. So I have tested
further actually available interpolators in Sextante and I verified that
spline method used by "Void filling" is actually one of the most
suitable among them. The same tool is faster than I believed two
days ago. :)
Instead, IDW or kriging interpolators needs a sensitivity analysis on
their specific parameters in order to have a more robust DTM generation.
Optimal results are not always guaranteed, because the use of an
interpolator could be suitable for a specific subset of data and not for
others.
For instance, "Complete grid" tool could be used in order to make a
fusion of DTM deriving from the application of different interpolation
techniques. In detail, this tool allows the user to specify the
interpolation method to be used.
It's important to keep in mind that there's not an universal interpolation
technique for all kind of data sources and any purpose.
Thanks for your attention.

Best regards,
Antonio

-- 
Antonio Falciano
http://www.linkedin.com/in/antoniofalciano