[GRASSLIST:1866] Re: i.ortho.photo on osx

Richard Greenwood Rich at GreenwoodMap.com
Sat Nov 22 22:18:25 EST 2003

At 09:47 AM 11/20/2003, Markus Neteler wrote:
>Our group has recitified 100+ images without problems, in terrible
>terrain (200-3500m) with an average error of 6 meters which is

That eliminates one of my theories - that the author of i.ortho.rectify 
assumed feet.

> > However, when I converted the vertical units to feet, the results were 
> correct.
>Mhhh. I think that both horizontal and vertical units should be identical.

Yes, so do I! Or some constant needs to be applied if the horizontal and 
vertical units differ, but I do not see any place in i.ortho.rectify where 
the vertical units are specified.

> > The example in your book uses Spearfish. I don't have Spearfish loaded
> > right now, but I am guessing that the elevation model is in feet. Possibly
> > I am wrong?
>No, the spearfish DEM is in meters:
>r.info elevation.dem
>  |   Data Description:
>  |    Elevation above mean sea level in meters for spearfish database

Yes, you are quite right. I loaded Spearfish and worked thru the example in 
your book and arrived at a satisfactory image rectification.

All of this is to say that I have gotten no closer to identifying the 
problem. If we rule out an error in the program logic, then it makes me 
think that the differences are in the definition of the location, but I do 
not see anything there that specifies a unit for vertical data.

I will keep looking at this, but any pointers would be appreciated.

Best regards,

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

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