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<DIV><FONT face=Arial size=2><SPAN
class=101470519-14092004>Greetings,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=101470519-14092004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=101470519-14092004>This is my first
post. I tried searching around for examples but didn't find much and mailman's
search capability is non-existant.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>So what's the secret
for using more than 4 gcps with gdalwarp?</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>I have 3 pieces of
imagery I'm mosaicing. I know the corners of each image. I created a single
non-projected tif of the three separate images. I computed where (in pixel
space) the top two corners of the first two images are in the resulting tif and
where the bottom two corners of the last image are. This resulted in 6 GCP
points. So I ran the following:</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>gdal_translate
-gcp 0 0 56.7468972222222 29.4295138888889 -gcp 859 0 56.9820861111111
29.4210638888889 -gcp 0 1363 56.7391 29.1199027777778 -gcp 859 1363
56.9705611111111 29.1071416666667 -gcp 859 2171 56.9677027777778
28.9774388888889 -gcp -gcp 0 2171 56.7381583333333 28.9917333333333
mosaic.tif mosaic_raw.tif</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>Then I
ran:</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004> </DIV>
<DIV><BR><FONT face=Arial size=2>gdalwarp -co "TFW=YES" mosaic_raw.tif
mosaic_new.tif</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004></SPAN><FONT face=Arial size=2>A<SPAN
class=101470519-14092004>nd got:</SPAN></FONT></DIV><FONT><SPAN
class=101470519-14092004></SPAN>
<DIV><BR><FONT face=Arial size=2>ERROR 1: Failed to compute polynomial equations
of desired order<BR>for provided control points.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>If I use -order 1 I
get a really screwing output.</FONT></SPAN></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004></SPAN><FONT face=Arial size=2>I<SPAN
class=101470519-14092004>f I remove the middle point and do:</SPAN></FONT></DIV>
<DIV><FONT><SPAN class=101470519-14092004></SPAN> </DIV>
<DIV><BR><FONT face=Arial size=2>gdal_translate -gcp 0 0 56.7468972222222
29.4295138888889 -gcp 859 0 56.9820861111111 29.4210638888889 -gcp 859 2171
56.9677027777778 28.9774388888889 -gcp 0 2171 56.7381583333333
28.9917333333333 mosaic.tif mosaic_raw.tif</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2>Then:</FONT></SPAN></DIV>
<DIV><BR><FONT face=Arial size=2>gdalwarp -co "TFW=YES" mosaic_raw.tif
mosaic_new.tif</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>I get a projected
mosiac of my images but it's not warped as I'd like.</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>So again my question
is what needs to be done to use higher order warping? What are the rules gcps
must follow?</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>I'm using
gdal1.2.1</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial size=2>Thanks in
advance,</FONT></SPAN></DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=101470519-14092004><FONT face=Arial
size=2>-ethan</FONT></SPAN></DIV></FONT></FONT></SPAN></BODY></HTML>