[GRASS-user] raster pixel value

[Nikos Alexandris]

* Francois Chartier <fra.chartier at gmail.com> [2019-03-10 10:56:40 -0400]:

>I am asking a question on the fundamentals not on a particular example on
>how the value within a raster cell is determined when multiple vector data
>points are located within a raster cell footprint.
>I use RST mostly and sometimes IDW for vector data points.

Then, from https://grass.osgeo.org/grass76/manuals/rasterintro.html:

"Raster input maps are automatically cropped/padded and rescaled (using
nearest-neighbour resampling) to match the current region."

and

"GRASS raster map processing is always performed in the current region
settings (see g.region), i.e. the current region extent and current
raster resolution is used. If the resolution differs from that of the
input raster map(s), on-the-fly resampling is performed (nearest
neighbor resampling). If this is not desired, the input map(s) has/have
to be resampled beforehand with one of the dedicated modules.

The built-in nearest-neighbour resampling of raster data calculates the
centre of each region cell, and takes the value of the raster cell in
which that point falls.

If the point falls exactly upon a grid line, the exact result will be
determined by the direction of any rounding error. One consequence of
this is that downsampling by a factor which is an even integer will
always sample exactly on the boundary between cells, meaning that the
result is ill-defined."

Likely there is more on the subject.

Nikos