[GRASSLIST:1792] Re: i.ortho.photo on osx

[Richard Greenwood]

Ian,

I ran into some unusual results that looked similar to yours. It was a 
while ago so I forget the exact details, but I got it working correctly by 
changing the Z units. My foggy recollection is that I supplied a DEM in 
meters, but my horizontal units were in feet, and the results were highly 
distorted. And changing everything to feet produced correct results. I you 
have not solved your problem yet, I would be happy to resurrect my project 
and see if I can provide a better description.

I do not think an elevation range of 540m should be a problem. I had a 
project with over 1500ft that came out very nicely.

Both of the projects that I did were on Mandrake Linux, but I doubt that 
your problems are rooted in OSX.

Best regards,
Rich


At 09:13 AM 11/17/2003, Ian Macmillan wrote:
>Markus, thanks for the response.  I do have a dem which covers the entire
>photo area.  It is a little larger in fact, is that a problem?  Should I 
>crop it
>so that it is the same size as the photo in area?  The dem is at 10m
>resolution, just like I want the projected orthophoto to be.  I made the DEM
>with s.surf.rst from a 30m dem, doesn't seem like that should make any
>difference from a "normal" dem.  In any case the elevation range is only ~540
>meters.  Is this too much?  What is the biggest elevation range that you have
>gotten to work?
>
>The r.univar report for the dem is here:
>Number of cells: 432276
>Minimum: 579.7407226562
>Maximum: 1119.2756347656
>Range:  539.535
>Arithmetic mean:  775.406
>Variance:  17639.4
>Standard deviation: 132.813
>Variation coefficient: 17.1282 %
>
>
>Thanks a bunch, ian
>
>
> >
> >
>
>Quoting Markus Neteler <neteler at itc.it>:
>
> > On Sat, Nov 15, 2003 at 12:38:05PM -0800, Ian Macmillan wrote:
> > > Hi all, anyone out there successfully used i.ortho.photo on max os x
> > (jaguar)?
> > > I have been having bad luck with it.  I consistently get a weird tiling
> > effect
> > > with highly distorted images.  A good example can be found here.
> > >
> > > www.uweb.ucsb.edu/~ian_macmillan/calico.tif
> > >
> > > I have a previous post that explains exactly what I did to get this image
> > > (1702).  As far as I can tell, I have done everything by the book.
> > Anybody
> > > have any advice?
> > >
> > > Thanks a bunch
> > >
> > > -ian
> >
> > Ian,
> >
> > a similar problem we also face (on Linux, so it's a bug in the 
> i.ortho.photo
> > library).
> >
> > Some things to check:
> > - do you have a DEM which covers the area of the target orthophoto,
> >   all at the same resolution?
> > - what's the elevation difference in that area
> >   (r.univar tells you min and max etc)
> >
> > We have the impression, that the algorithm is somewhat unstable in regions
> > with a large elevation range.
> >
> > Markus Neteler
> >
>
>
>-----------------------------------------------------
>Ian MacMillan
>Geological Sciences-UCSB


Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com