[GRASSLIST:4759] Re: i.rectify doesn't produce an correct output

[Eric G. Miller]

On Thu, Oct 17, 2002 at 03:26:39PM +0200, Rado Bonk wrote:
> Hello GRASSusers,
> 
> I came into the problems using i.rectify command. My area of interest (AOI) is
> 200mx3000m (res=1m, projection -x,-y), however this belt is start at SE
> and ends at NW corner of the region. Thus there are a lots of NULL
> cells outside the AOI. To decrease the amount of NULL
> cells (for using the AOI in R language) I want to rectify (rotate) the
> belt into a horizontal position using lower right corner as a point of
> rotation. The target location is x,y, res=1m.
> 
> i.rectify finish the job without sending an email to localhost, and:

Sounds like i.rectify crashed for some reason (disk full?).

> 1. there is a output raster in cell directory with zero filesize

If floating point, this is normal.

> 2. output file is missing in cellhd directory
> 3. output file is missing in cell_misc directory
> 4. output file is missing in cats directory
> 5. output file has non zero filesize in fcell directory but r.support,
> and r.mapcalc don't work on it.

It probably is incomplete because i.rectify didn't complete correctly.
It's hard to say why.

> Is the -x,-y at original LOCATION, or reasonable fine resolution a problem? Is there a
> way in GRASS to rotatea region by an arbitrary angle (I can imagine that
> using r.proj magic)

There's the m.rot90 program (only 90 degree rotations).

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