Dave,<br><br>The reason you have lat/lon values for each pixel is because they may not be aligned exactly.<br>Even though it is not very 'efficient', you have to define the GCPs for each pixel with the lat/lon values of that pixel. Then you use gdalwarp while forcing use of these GCPs to combine all the images.<br>
<br>How are the lat/lon values stored?<br><br><div class="gmail_quote">On Sun, Jul 22, 2012 at 7:44 PM, David Hoese <span dir="ltr"><<a href="mailto:dhoese@gmail.com" target="_blank">dhoese@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Sure, pixels were probably not the best
word to use. I have 15 points(elements) per scan line per
"variable" directly from an aircraft instrument. So I might have
a 15 element array of brightness temperatures, a 15 element array
of latitudes corresponding to those points in the BT array, and
another 15 element array of longitudes corresponding to those
points in the BT array. So the first element in the brightness
temperature(BT[0]) array represents an area of the earth located
at lon[0],lat[0] (I'm actually not sure if its the center of the
area or the corner, but at the moment that doesn't matter).<br>
<br>
Does that make sense?<br>
<br>
-Dave<div><div class="h5"><br>
<br>
On 7/21/12 9:46 AM, Chaitanya kumar CH wrote:<br>
</div></div></div><div><div class="h5">
<blockquote type="cite">Dave,<br>
<br>
You said that you have lat/lon values for each pixel. Can you
explain?<br>
<br>
<div class="gmail_quote">On Fri, Jul 20, 2012 at 8:44 PM, David
Hoese <span dir="ltr"><<a href="mailto:dhoese@gmail.com" target="_blank">dhoese@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> I'm attempting to put
aircraft scan data into geotiffs (1-3 scanlines each) and
then use gdal_merge.py to combine them into one large
geotiff that has the entire aircraft's path. The scan lines
are 15 pixels wide and taken every 10 seconds, the geotiffs
are wgs84 lat/lon, and I have lat/lon values for each
pixel. To handle the case when the aircraft isn't flying
straight north I think I have to use the 2 rotation
parameters in the affine geotransform, is that right? I
don't have any test cases, but I think if I don't use
rotation anything that reads the geotiff will think that the
image is square(aligned) in lat/lon space.<br>
<br>
Whether or not I need to use this, can someone explain to me
how to use the rotation coefficients? What are the actual
values of the coefficients supposed to be? I couldn't find
a good example and I couldn't get any basic situations to
make sense, like a 2x3 array turned 45 degrees. I used
these equations:<br>
<pre> Xgeo = GT(0) + Xpixel*GT(1) + Yline*GT(2)
Ygeo = GT(3) + Xpixel*GT(4) + Yline*GT(5)</pre>
<br>
And lastly, does gdal_merge.py handle rotation? I checked
the source and it doesn't ever seem to use elements 2 and 4
in its calculations.<br>
<br>
Thanks for any help.<br>
<br>
-Dave<br>
</div>
<br>
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</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Best regards,<br>
Chaitanya kumar CH.<br>
<br>
<a href="tel:%2B91-9494447584" value="+919494447584" target="_blank">+91-9494447584</a><br>
17.2416N 80.1426E<br>
</blockquote>
<br>
</div></div></div>
</blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br><br>+91-9494447584<br>17.2416N 80.1426E<br>