[GRASS-user] problem with nnbathy interpolation

[lorenzo benvenuto]

Dear lists,

I'm working with the nnbahty interpolation (which uses the libratry
https://github.com/sakov/nn-c) and I've some troubles; what I expect is
that the interpolated raster map has the same value in the initial points:

-using GRASS 6.4 the interpolation works fine (so the interpolated raster
map has the same value of the initial points), but I can only run
r.surf.nnbathy (and not v.surf.nnbathy);

-using GRASS 7.4 the interpolation doesn't work fine (so the interpolated
raster map doesn't have the same value of the initial points), both using
v.surf.nnbathy and r.surf.nnbathy.

For example, I'm working in a WGS84 lat/lon location with temperature data
and I have:

-Value of inital point = 287.039
-Value of raster interpolated map (cheked on the control point) = 286.342

Actually I expected to find exactly the value of the initial point (i.e.
287.039).

As far as I understood the module nnbathy (both r.surf.nnbathy and
v.surf.nnbathy) exports the initial vector or raster map into an ASCII
file, than computes the interpolation using 'nnbathy.c' (which is in the
repository), and lasty inport in GRASS (r.in.ascii) the interpolated file.
What I think is that GRASS 7.4 makes some errors while exporting input file
or while importing interpolated ASCII file.

Do you have any suggestions?

Lorenzo
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