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<TITLE>[Gdal-dev] GDAL 1.2.2 Released</TITLE>
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<DIV id=idOWAReplyText74790 dir=ltr>
<DIV dir=ltr><FONT face=Arial size=2>Well I've done some good GDAL documentation
reading in the past couple days trying to get a handle on what I'm trying
to do with respect to GDAL's data model and I'm left with more questions than
answers.</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>I've boiled them down to one which if I can
get a handle on I might be to conceptually work my way through the
rest.</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>Being pretty ignorant I figured that
gdal's GCP's support could infer a projection. Which means I believed that
by providing geographic coordinates and pixel/line coordinates that GDAL
would some how infer a custom projection for my input data.</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>Is this truly a misconception?</FONT></DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=Arial size=2>The documentation for <FONT
face="Times New Roman" size=3>GDALCreateGenImgProjTransformer seems to suggest
this but I can't really find any references to how GCPs need to be related
spatially for it to work or whether my source needs to be in a known
projection.</FONT></FONT></DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>My data is reduced resolution raw satellite imagery. By raw I mean
there's been no ortho-rectification. In real world coordinates my pixel size can
vary a lot. </DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>I do have lots of useful information about my data. I have
ephemeris, attitude, bearing angle and off nadir angle data. I also have
anywhere from 4 to 40 geographic coordinates that define the polygon of the
strip (my GCP's) depending on the length of the strip. Each strip can often bend
and stretch through out it's scan.</DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>So anyway it seems to me I have enough to define a unique
projection for each strip of satellite imagery. My question is do I really need
to go through all of this? I'm not looking for the most accurate projection but
I'm looking for a better way to do it than I am currently.</DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>So the utility gdalwarp doesn't like my GCP's for higher order
warping and produces an awkwardly placed warped image when using -order 1.
The only thing I can think of is that I have some misconception of how to
classify my data's coordinate system, I'm doing something wrong with
preparing it or I need to look into the utility that initially generated the
4-40 GCP's of this data.</DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>Thanks,</DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>-ethan</DIV>
<DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV>
<DIV dir=ltr> </DIV></DIV>
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