[Qgis-developer] INterpolation plugin: lines structure and break lines?

[Marco Hugentobler]

Hi Paolo

Structure lines and break lines are considered in the generation of the TIN 
(IDW, by its nature, cannot consider linear elements). 

Lets say you have elevation data that you want to be on the digital surface 
(lake borders, contour lines, valley lines, ...). The code modifies the 
triangulation such that no edge crosses a structure / break lines (known as 
constrained delaunay triangulation).

The difference between break- and structure lines is that the first means a 
sudden change in slope (where the surface is not continuously differentiable) 
and the second a slow change. At the moment, in the interpolation plugin, 
there is only linear interpolation for TINs and it behaves the same in both 
cases. I have some code from my phd that provides cubic interpolation an that 
makes a difference. I plan to bring this code into the interpolation plugin, 
but it uses some old Qt3 container classes and therefore needs cleanup (maybe 
at the hackfest ;-) ).

For an easy introduction to the subject, see my phd (or some of the references 
listed): http://www.dissertationen.unizh.ch/2004/hugentobler/diss.pdf


Regards,
Marco

Am Freitag, 9. Oktober 2009 16.35:04 schrieb Paolo Cavallini:
> Hi all (especially Marco).
> I do not understand whet is the meaning of the above mentioned options for
> interpolation. Is there some documentation?
> All the best.

-- 
Dr. Marco Hugentobler
HUGIS - GIS programming and consulting
Webereistrasse 66
CH-8134 Adliswil
marco at hugis.net
http://homepage.hispeed.ch/hugis