[GRASSLIST:1778] Re: i.ortho.photo on osx

Ian Macmillan ian_macmillan at umail.ucsb.edu
Mon Nov 17 11:13:41 EST 2003

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

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