[GRASS5] [bug #859] (grass) raster data at lower resolution: no resampling...

[Markus Neteler]

On Tue, Nov 27, 2001 at 10:31:04AM -0500, Helena Mitasova wrote:
> Markus Neteler wrote:
> 
> > O.k. - the problem is that I have no idea what "resampled" means in
> > this case. It seems that we have to study the related sources.I just want
> > to understand what's happening.
> 
> I guess you should really look at the source and then write what you have found
> into the prog manual and users manual (probably for g.region entry).
> Does anybody know what it is doing already, to save Markus some time?

Well,  I need assistance since I don't understand the code :-)
It should be here:
src/libes/gis/get_row.c
[...]
 *   Step 2:  Convert the data into a CPU readable format, and subsequently
 *            resample the data. the data is stored in a second intermediate
 *            buffer (the type of the data in this buffer is Y)....
[...]

Maybe someone professional looks with doxygen or whatever at the
dependencies. Is it done in XDR or somewhere else? And what is done?
 
> > Does it make sense print a warning in this case? To make the user
> > aware that the resolution doesn't match?
> > At least when exporting data or using r.mapcalc this is quite important.
> 
> I agree with that, but I am not sure how much work it would be.
> It would certainly be beneficial if r.mapcalc let user know
> e.g. when computing C=A+B+D it could write : Warning, resampling map A to match
> the resolution.
> When exporting, it would be useful too. In r.flow, where it really matters,
> we just say that "your resolution does not match the current resolution" and exit
> so the user has to fisrt change his region to that of the elevation input or
> resample/reinterpolate
> his elevation. So it is really application and data dependent.
> 
> Helena

Thanks for your comments. I fear we have to dig into the code to
find out the current implementation. From that we may decide if and
where to implement user notifications.

Markus