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.
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:
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:
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:
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.
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:
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.
Dear Mrs. Patrasova, Mr. Metz, Mr. Kudrnovsky, Mr. Neteler,
Thank you all for the replies!!
@ Mr. Metz:
So curvature analysis in GRASS are neither Gaussian nor Mean curvature analysis types? Did I understand that correctly?
@ Mr. Kudrnovsky, Mrs. Patrasova:
Both source codes seem to mention the profile and tangential curvature.
@Mr. Neteler:
The book is a bit expensive (for my country) but seems to be quite good as well!
I also not sure just looking at the equations would help me identify whether it is Gaussian or Mean curvature type, due to my non-mathematical non-GIS background.
On Wed, Sep 14, 2016 at 1:07 AM, Djordje Spasic <issworld2000@yahoo.com> wrote:
Dear Mrs. Patrasova, Mr. Metz, Mr. Kudrnovsky, Mr. Neteler,
Thank you all for the replies!!
@ Mr. Metz:
So curvature analysis in GRASS are neither Gaussian nor Mean curvature
analysis types? Did I understand that correctly?
You can do both in GRASS. Get the principal curvatures you need with
one of the previously mentioned modules, then calculate Gaussian (K1 *
K2) and/or Mean ((K1 + K2) / 2) curvature.
Markus M
@ Mr. Kudrnovsky, Mrs. Patrasova:
Both source codes seem to mention the profile and tangential curvature.
@Mr. Neteler:
The book is a bit expensive (for my country) but seems to be quite good as
well!
I also not sure just looking at the equations would help me identify whether
it is Gaussian or Mean curvature type, due to my non-mathematical non-GIS
background.
On Wed, Sep 14, 2016 at 9:20 AM, Markus Metz
<markus.metz.giswork@gmail.com> wrote:
On Wed, Sep 14, 2016 at 1:07 AM, Djordje Spasic <issworld2000@yahoo.com> wrote:
Dear Mrs. Patrasova, Mr. Metz, Mr. Kudrnovsky, Mr. Neteler,
Thank you all for the replies!!
@ Mr. Metz:
So curvature analysis in GRASS are neither Gaussian nor Mean curvature
analysis types? Did I understand that correctly?
You can do both in GRASS. Get the principal curvatures you need with
one of the previously mentioned modules, then calculate Gaussian (K1 *
K2) and/or Mean ((K1 + K2) / 2) curvature.
Related FWD from Helena, supporting above:
On Wed, Sep 14, 2016 at 1:08 AM, Helena Mitasova <hmitaso@ncsu.edu> wrote:
No it is neither gaussian, nor mean. v. surf.rst outputs also mean. But any
curvature can be computed using the second order derivatives output and map
algebra. It would be also relatively easy to add mean and gaussian curvature
to the outputs.