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extend r.slope.aspect to compute the values at the edges #144

Open landam opened 5 years ago

landam commented 5 years ago

Reported by hellik on 4 Jan 2015 18:37 UTC taken from the ML

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

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.

GRASS GIS version and provenance

svn-trunk

Migrated-From: https://trac.osgeo.org/grass/ticket/2526

landam commented 5 years ago

Modified by neteler on 4 Jan 2015 21:39 UTC

landam commented 5 years ago

Comment by neteler on 5 May 2016 14:08 UTC Milestone renamed

landam commented 5 years ago

Comment by neteler on 28 Dec 2016 15:04 UTC Ticket retargeted after milestone closed

landam commented 5 years ago

Modified by @landam on 5 May 2017 20:40 UTC

landam commented 5 years ago

Comment by @landam on 1 Sep 2017 20:28 UTC All enhancement tickets should be assigned to 7.4 milestone.

landam commented 5 years ago

Comment by neteler on 26 Jan 2018 11:40 UTC Ticket retargeted after milestone closed

landam commented 5 years ago

Comment by mmetz on 29 Apr 2018 14:22 UTC Implemented in https://trac.osgeo.org/grass/changeset/72653 with a new -e flag to compute values at edges, idea and method from gdaldem -compute_edges.

landam commented 5 years ago

Modified by neteler on 12 Jun 2018 20:48 UTC

landam commented 5 years ago

Comment by @landam on 25 Sep 2018 16:51 UTC All enhancement tickets should be assigned to 7.6 milestone.

landam commented 5 years ago

Comment by @landam on 25 Jan 2019 21:07 UTC Ticket retargeted after milestone closed