[GRASSLIST:1792] Re: i.ortho.photo on osx
Rich at GreenwoodMap.com
Mon Nov 17 23:07:00 EST 2003
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.
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
>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
>Arithmetic mean: 775.406
>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
> > 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
Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
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