i.rectify

[Malcolm Williamson]

On Wed, 24 Sep 1997, Jean-Marc Chofflet wrote:

> Hello dear GRASS users!
> 
> I've already sent this message a month ago and
> didn't get any answer...
> It might be it didn't reach the right destination,
> or my questions may be irrelevant (;-(...
> 
> 
> I'm a new GRASS (under Linux) user and have 2 problems :
> 
> First of all, I'm using GRASS but not only GRASS... which
> means I'd like to be able to use my datas under various softwares.
> So, I'm using the different GRASS progs to import/export data.
> 
> My first problem is that r.out.tga is producing huge files (24 bits
> images) 
> although one uses only (mainly ?) 8 bits images with GRASS... Is there
> another
> raster
> export prog which can produce 8 bits images (e.g. r.out.gif)?

Have you looked at r.out.tiff? This produces 8-bit tiffs only.

> 
> My second problem is less obvious : I've scanned a map in 15 images.
> Before digitizing it (with another software), I've i.rectified each of
> them
> (i.rectify2, 3rd order, at least 30 GCP's per image). When I try to
> put the 15 rectified images together (after an r.out.tga) in any
> software 
> (I'm now using CorelXARA under Windows) there are some distorsions, but
> if
> I first r.patch those and then r.out.tga the result, it fits perfectly!
> I thought the images produced by i.rectify2 were... rectified!!!
> You could say : "never mind, use r.patch!". Yes, except that it would
> produce a file my poor Pentium 133, 64 MB of RAM and 4GB of HDD wouldn't
> dare
> to just look at it!

Could you give a little more information about the images that you are 
scanning? Unless they are non-ortho-rectified aerial photos, chances are 
that you really only need a first order rectification, simply to 
geo-reference them. I'm really unclear about whether you were r.patch-ing 
them before or after rectification.

	-Malcolm


> 
> Thanks by advance
> 
> 
> ***************************************************
> *                                                 *
> *     JM Chofflet                                 *
> *                                                 *
> *     ERA 41 du CNRS       7, rue Gaston Couté    *
> *     3, rue Michelet      F75018 Paris           *
> *     F75006 Paris                                *
> *                                                 *
> *     tel off. : +33 (0)1 53 73 71 08             *
> *     tel home : +33 (0)1 46 06 88 59             *
> *     fax      : +33 (0)1 44 07 01 79             *
> *     Mailto:chofflet at asterix.univ-paris1.fr      *
> *                                                 *
> ***************************************************
>