[GRASS5] bug in d.what.rast

[Glynn Clements]

GRASS wrote:

> -c bug fixed.

Only in the head; the release branch still has the old version.

> > > > Also, I'm suspicious of Huidae's "fix" in 1.3:
> > > >
> > > > -    n_row = (int) ((cellhd.north - north) / cellhd.ns_res);
> > > > -    e_col = (int) ((east - cellhd.west) / cellhd.ew_res);
> > > > +    n_row = (int) ((cellhd.north - north) / window->ns_res);
> > > > +    e_col = (int) ((east - cellhd.west) / window->ew_res);
> 
> It is different if the window's resolution is changed by "g.region *res=".

I know; but:

> > > > Either of:
> > > >
> > > >   n_row = (int) ((cellhd.north - north) / cellhd.ns_res);
> > > >   e_col = (int) ((east - cellhd.west) / cellhd.ew_res);
> > > > and:
> > > >   n_row = (int) ((window->north - north) / window->ns_res);
> > > >   e_col = (int) ((east - window->west) / window->ew_res);
> > > >
> > > > make sense, depending upon whether you want coordinates in map cells
> > > > or window cells. But I can't see any obvious significance to the
> > > > values returned by the existing code.

> -c option was designed to get the row/col of the map for non-GRASS models.
> It was difficult to get the coordinates of the interesting points, which do
> not have any info to get the locations, by counting cells.

In which case, it should probably be using cellhd.{ns,ew}_res, and not
window->{ns,ew}_res.

> > 2. When specifying multiple maps, the window row/col are the same for
> > all of them, whereas the map row/col varies with a map's boundaries
> > and resolution.
> 
> I didn't consider multiple maps. :-(  If it's needed, it is not difficult to
> implement it.

It's probably not that important.

What is important is that -c returns meaningful values, and that the
significance of those values is documented.
 
> > However, if the intention is to use window rows/cols, there isn't any
> > point in passing the map name or mapset to show_utm(). Those values
> > are only used to retrieve the map's Cell_head, which is only required
> > if you want to report map rows/cols.
> 
> The map's Cell_head is required to get the boundary of the map.  The row/col
> is calculated from this boundary.

Sure; but that implies that you should also be using the resolution
from the Cell_head, not from the window.

-- 
Glynn Clements <glynn.clements at virgin.net>