Georeferencing Maps [was GPS and airspace]

"John Clonts" wrote in message
om...

Kyler,

This is the input I got from J.G. on the OziUsers list, regarding the
above:

begin quote
I took a look at the goetiff tags for the two images and I think I
see the problem. The full image is specifying a key:

ProjNatOriginLongGeoKey (Double,1): -100

While the smaller image does not even have that key. Somehow, the
smaller image is using the tag:

ProjFalseOriginLongGeoKey (Double,1): -100.583333

These can't both be right. I'd say the full image is the right one,
since it loads fine in not just Ozi, but other programs too, while
the smaller image does not work in other programs. I'm pretty
certain that the ProjNatOriginLongGeoKey is only supposed to be used
in cases where the prime meridian is not the familiar 0 degrees
longitude value. Technically, the math may work, to subvert the
function of that tag and then specify the ProjFalseOriginLongGeoKey
as 0.0, but it's highly irregular. Listgeo is able to deal with it,
by translating the natorigin key to it's equivalent falseorigin key,
but programs generating geotiff files should not rely on geotiff
readers to do this.

All that said, you can fix these keys. If you redirect the output of
the listgeo program to a file, you can edit that file with any
ordinary text editor and reinstall it into the geotiff file, using
the geotifcp program, which is part of the zip file I referred to
previously.

J.G.
end quote

Hello Kyler,

FYI, I patched the tags in my test file (from
https://aviationtoolbox.org/Members/...ul_Y=-676347.0)
with geotifcp per J.G.'s instructions, and Oziexplorer is happy with that
image now. Do you know if changing your generation code would be
appropriate, and/or cause other problems with other software?

Cheers,
John