[GRASS-dev] r.fill.gaps porting

[Benjamin Ducke]

Hi,

Regarding the the smoothing, the description
states:

"Flags:

[..]

-p
    Preserve original cell values
    By default original values are smoothed"

The first paragraph under "DESCRIPTION" says:

"Alternatively, setting the -p flag will preserve the original cell values."

Is that not clear enough? If you want then I can add
a more prominent statement at the beginning of the
help page.

The thing is: I originally developed this module for
gradiometer data. That data is very noisy and has
high local variation. Interpolating that type of
data while preserving original measurements will
usually result in unsatisfactory output. Also note
that the smoothing increases with the interpolation
radius. For tiny holes in LiDAR data, try "distance=1"
or "2". Of course, LiDAR data probably has different
properties and does not need low-pass filtering
like gradiometer data. So try "-p" to preserve the
original values.

An alternative would be to invert the behaviour of
the module and assume "-p" by default.

I don't work with LiDAR data myself, but I would very
interested to know your results!

Best,

Ben


On 15/04/17 13:51, Maris Nartiss wrote:
> Hello,
> it is nice to see porting of old addons.
> As you added an example with LiDAR data - it is too large. Reduce its
> size as default module help tab is much more narrow.
> A bigger problem is the modules description - as I was checking the
> output of module, it is reinterpolating all values instead of just
> filling gaps. Thus the result is smoothened instead of just being
> filled. This is in a sharp contrast to r.fill.nulls and thus should be
> stressed out.
> 
> Thanks for a good work!
> Māris.
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-- 
Dr. Benjamin Ducke
{*} Geospatial Consultant
{*} GIS Developer

Spatial technology for the masses, not the classes:
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