[GRASS-dev] Unresolved directions in r.fill.dir

[Markus Metz]

On Sun, Nov 26, 2017 at 10:12 PM, Anna Petrášová <kratochanna at gmail.com>
wrote:
>
> On Sun, Nov 26, 2017 at 4:04 PM, Markus Metz
> <markus.metz.giswork at gmail.com> wrote:
> > Hi Vaclav,
> >
> > On Sun, Nov 26, 2017 at 1:31 AM, Vaclav Petras <wenzeslaus at gmail.com>
wrote:
> >>
> >> Hi all,
> >>
> >> r.fill.dir with the bellow artificial DEM leaves part of the directions
> >> unresolved and this area is marked in areas, although the area is
filled in
> >> the output. Here is the code to reproduce:
> >>
> >> g.region n=220750 s=220000 w=638300 e=639000 nsres=1 ewres=1 rows=750
> >> cols=700 -p
> >> r.mapcalc "hills = 500 * sin(row()) + 500 * sin(col())"
> >> r.fill.dir input=hills output=filled direction=directions areas=areas
> >>
> >> In r71809, I have committed a fix which transforms these unresolved
> >> directions to NULLs because in the previous implementation (current
7.4svn
> >> and older) internal representation of angles was leaking outside of the
> >> module.
> >>
> >> I have 2 questions:
> >>
> >> Should I backport r71809 to 7.4?
> >
> > For me, the fix makes sense.
> >>
> >> Should we pursue this issue further to resolve why these edge cases are
> >> not resolved, although they are filled? Does anybody has suggestions
at this
> >> point? (Paper with the method is linked in the doc.)
> >
> > I don't think it is worth the pursue the issue of directions any
further.
> > The module is based on rather old, not to say outdated, methods from the
> > 1980's. These methods were developed for DEMs created from contour lines
> > which in turn were determined by land surveyors. Back then there was
nothing
> > like SRTM or LiDAR.
> >
> > r.hydrodem offers a more advanced method to remove sinks by a
combination of
> > filling and carving.
>
> Why don't we move r.hydrodem to core? Is there any reason to keep it in
addons?

r.hydrodem needs a testsuite to be moved to core.

Markus M
>
> Anna
>
> >
> > Directions can also be obtained with r.slope.aspect or with the
hydrological
> > modules r.watershed, r.stream.extract, r.terraflow. Regarding hydrology,
> > main flow directions may differ between modules and settings and to
> > directions from r.slope.aspect, but all of them are valid according to
the
> > logic of the underlying algorithm and settings.
> >
> > Markus M
> >>
> >> Thank you,
> >> Vaclav
> >>
> >> https://trac.osgeo.org/grass/changeset/71809
> >> https://grass.osgeo.org/grass74/manuals/r.fill.dir.html
> >>
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> >
> >
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