[GRASS-user] Error using Georectify tool

[Markus Metz]

On Sat, Nov 27, 2010 at 12:23 PM, Jenny Turner
<jennyturner1980 at gmail.com> wrote:
> Hi
>
> I'm using GRASS GIS 6.4.0 (stable version) in Windows (because my Univ made
> a few addaptations and modules to be used in my final project) but I'm
> having some difficulties in using Georectify tool.
>
> After I select 3 points, I press Recalculate RMS Error (and I get the image
> that I have attached to the email). THis is impossible to have 0,0 as error
> (in this case).

No, because the RMS errors will always be zero if the number of points
is equal to the minimum number of points required for the selected
order, here 3 points for first order.

> POINTS file <D:\data\Area\scale\group\ai\POINTS> saved
> But, then I press Georectify and It freezed all Interfaces and I got, in the
> top of each one, (Not Responding)... I waited 10 minutes (it sould take less
> than that). And still not responding...

Ho long does georectification take if you use i.rectify directly from
the source location/mapset?

>
> Another question:
> If my source (to be georreferenced) data has a resolution of 10 meters and
> my target (already georreferenced) as 30 meters resolution and my active
> mapset is 10 meters.. Georreferenced output will have which spatial
> resolution?
>
If you choose 'clip to computational region in target location', the
computational region in the target location+mapset will be used.
Otherwise i.rectify estimates the minimum target region required to
hold the source image and estimates a resolution corresponding to the
image resolution.

Markus M