On Tue, Sep 13, 2016 at 5:48 PM, Markus Neteler <[email protected]> wrote: > On Tue, Sep 13, 2016 at 4:02 PM, Anna Petrášová <[email protected]> wrote: >> On Tue, Sep 13, 2016 at 7:58 AM, Helmut Kudrnovsky <[email protected]> wrote: >>> georges wrote >>>> Hello, >>>> >>>> I would like to know whether raster curvature analysis in GRASS >>>> is Gaussianor Mean curvature analysis? >>>> https://en.wikipedia.org/wiki/Gaussian_curvature >>>> https://en.wikipedia.org/wiki/Mean_curvature >>>> >>>> This GRASS 7.2 manuals page mentions that raster curvature analysis can be >>>> conducted in direction of steepest slope and in the direction of the >>>> contour tangent, therefor distinguishing two curvature options: profile >>>> and tangential. >>>> >>>> Still are these two Gaussian or Mean curvatures? >>>> >>>> Thank you for the reply. >>> >>> I can't tell you directly which algorithm is used. >>> >>> fortunately GRASS GIS is open source; so maybe have a look at the source >>> code to check: >>> >>> r.slope.aspect: >>> >>> https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.slope.aspect/main.c >>> >>> or >>> >>> r.resamp.rst >>> >>> https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.resamp.rst/main.c >>> >>> HTH >> >> also r.param.scale: >> https://trac.osgeo.org/grass/browser/grass/trunk/raster/r.param.scale/
IIUC, Gaussian and Mean curvatures are based on principal curvatures. Principal curvatures in turn are calculated for an orthonormal basis. r.param.scale calculates different principal curvatures for different bases (z-axis and the surface normal vector). You can obtain Gaussian or Mean curvatures from these principal curvatures. Markus M > > > You find the formulas used for the r.slope.aspect and r.resamp.rst > implementations in the GRASS book, 3rd edition, 2008, Springer, > Appendix pages 371-376. > > Best, > Markus > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
