[GRASSLIST:1922] Re: i.ortho.photo on osx

[Markus Neteler]

On Fri, Nov 28, 2003 at 05:59:43PM -0700, Richard Greenwood wrote:
> At 10:07 AM 11/26/2003, Markus Neteler wrote:
> 
> >Reference:
> >http://grass.itc.it/pipermail/grassuser/2003-November/010893.html
> >
> >Above problems should be fixed now (in 5.3-CVS). Reason was
> >that a DEM of FCELL type was not read properly.
> >In case of such troubles either update i.ortho.photo or use
> >'r.recode' to make the DEM of DCELL type.
> 
> Markus, Ian;
> 
> I revisited my problematic project, converted to DCELL and it worked very 
> nicely. Thanks Markus! But, I am confused on FCELL versus DCELL. I assumed 
> that my metric DEM was integers and that converting to feet created a 
> floating point, or double precision DEM, thus avoiding the problem you 
> describe above. But what is the difference between FCELL and DCELL?

[ already explained ] 

> An important note (especially for Ian), my Overall rms error was 17.92 with 
> my DEM in feet, but went down to 1.71 with a DCELL DEM in meters. I believe 
> this is because the vertical units must be the same as the horizontal 
> units.

I think yes.

> In other words, by converting to feet I was able to bypass the 
> problem Markus has described and create a visually acceptable ortho 
> rectification, but not a 'correct' rectification. I had attributed the high 
> rms error to bad data, but I no longer believe that to be the case.
> 
> Two 'off topic' notes:
> 
> Markus - I have a 5.0.3 cygwin binary distribution at 
> www.greenwoodmap.com/grasss (see configure.log for configure options) I 
> have been using it for about two weeks and I am reasonably confident with 
> it. In my limited testing, PostgreSQL seems to be working, too!

Thanks, I am downloading right now, will be in
 http://grass.itc.it/grass5/binary/windows_cygnus/wingrass_xserver/
soon.
 
[...]

 Markus