#2526: extend r.slope.aspect to compute the values at the edges

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Reporter: hellik | Owner: grass-dev@…

Type: enhancement | Status: new

Priority: normal | Milestone: 7.1.0

Component: Raster | Version: svn-trunk

Keywords: slope | Platform: All

Cpu: All |

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taken from the ML

http://lists.osgeo.org/pipermail/grass-dev/2015-January/072779.html

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Another way would be to modify r.slope.aspect to compute the values at the

edges - a second order polynomial min.square approximation

is used to estimate the derivatives in r.slope.aspect (you get the well

known differencing function when you do the math) and it can be used also

to compute the values at the edge cells, but I had no luck convincing

others that it is the right thing to do.

I believe that any reasonable estimate is better than the current

shrinking region (in r.flow we just propagate the same values to the

edges), but that does not seem to be the consensus.

Also, implementation for the edges is not straightforward because of how

GRASS works with rows, but a smart developer could certainly do it.

}}}

it would be nice that r.slope.aspect compute the values at the edges, at

least as an option. I agree that any reasonable estimate is better than

the current shrinking region.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/2526>

GRASS GIS <http://grass.osgeo.org>