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Hi All,<br>
Even's advice below (for cropping) was perfect for what I wanted, but
now I see that the original georeferencing of the scanned images was
not that great.<br>
<br>
I have pixel values for the (skew) LatLong corners, but I cant fathom
out how to use these as GCPs to re-geo-reference the scans.<br>
The following introduces the GCPs into the image, <br>
gdal_translate -gcp 361.125702 529.504089 20.00 -28.25 -gcp 6142.089844
530.520996 20.25 -28.25 -gcp 6129.833496 7090.170410 -20.25 -28.50 -gcp
359.345825 7085.267090 20.00 -28.50 2820AC_1990_ED2_GEO.TIF
../2820ac_gcp.tif<br>
<br>
but running:<br>
gdalwarp -te 20.00 -28.50 20.25 -28.25 2820ac_gcp.tif 2820ac_warp.tif<br>
does not give the desired results.<br>
<br>
<br>
What is the correct way to improve the georeferencing of and existing
GeoTIFF, using GCPs?<br>
<br>
Thanks & regards,<br>
Zoltan<br>
<br>
<br>
<br>
<br>
Zoltan Szecsei wrote:
<blockquote cite="mid:4BC19433.30505@geograph.co.za" type="cite">
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Hi Even,<br>
I think I have spent too much time using older proprietary software. I
figured the image would have to be deskewed before using "te" option,
but now that you mention it, it makes sense that gdal would (should)
look at all the tfw & embedded parameters before it willy-nilly
crops for the output extents.<br>
(So yes, it should "just work")<br>
<br>
I'll give it a bash on one of the scans. <br>
<br>
Thanks & regards,<br>
Zoltan<br>
<br>
Even Rouault wrote:
<blockquote cite="mid:201004111110.45295.even.rouault@mines-paris.org"
type="cite">
<pre wrap="">Zoltan,
I'd use something like : gdalwarp -te 24.75 -34.25 25.00 -34.00 src.tif
out.tif
In your case, you just need to be able to analyze the image name, compute
xmin, xmax, ymin, ymax, build the gdalwarp line and spawn the new process. So
I think you could use any programming/scripting language you like. I'd
personnaly use Python and the GDAL Python bindings (other well supported
binding languages are Perl, CSharp and Java). The advantage is that you
wouldn't need to make any assumption on the structure of the image name and
could get its spatial extent in a more reliable way.
Le Sunday 11 April 2010 08:49:28 Zoltan Szecsei, vous avez écrit :
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
I'm using viewing software that cannot rotate images on the fly (see
non-zero rotation parameters in TFW below.)
I have almost 2000 scans in GeoTIFF that I hence need to deskew and also
want to crop.
I've been looking at gdalwarp, but can't see an obvious way to
bash-script deskewing, so please can someone give me a pointer where to
start/research.
Thanks in advance,
Zoltan
Each image represents a quarter degree square and I can use the image
name to calculate the Lat Long values of the 4 corners.
3424bb is:
TL: 34.00S 24.75E
TR: 34.00S 25.00E
BR: 34.25S 25.00E
BL: 34.25S 24.75E
I want to crop the image on these quarter degree boundaries, and deskew it.
<removed> as msg size exceeded 50k (was 70K)
The attached jpeg is a much-reduced sample, so you can get the idea of
what they look like.
</removed>
I have the following information at hand:
###########################################################################
###### ls -la:
geograph geograph 5231378 2006-09-13 17:28 3424BB_1999_ED3_GEO.TIF
###########################################################################
###### Pixel positions of the 4 quarter degree square corners are at:
TL 1090.489746 1226.423828
TR 6546.639160 1220.069458
BR 6546.430176 7770.449219
BL 1106.605347 7776.899902
###########################################################################
###### cat 3424BB_1999_ED3_GEO.tfw
0.0000459558
-0.0000000502
-0.0000000963
-0.0000381753
24.6998662805
-33.9529134036
###########################################################################
###### gdalinfo 3424BB_1999_ED3_GEO.TIF
Driver: GTiff/GeoTIFF
Files: 3424BB_1999_ED3_GEO.TIF
Size is 7796, 10629
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.2572235629972,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
GeoTransform =
24.6998433507502, 4.595577857784442e-05, -9.634765806162092e-08
-33.95289429083027, -5.021067810400542e-08, -3.817529052330018e-05
Metadata:
AREA_OR_POINT=Area
TIFFTAG_XRESOLUTION=300
TIFFTAG_YRESOLUTION=300
TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 24.6998434, -33.9528943) ( 24d41'59.44"E, 33d57'10.42"S)
Lower Left ( 24.6988193, -34.3586595) ( 24d41'55.75"E, 34d21'31.17"S)
Upper Right ( 25.0581146, -33.9532857) ( 25d 3'29.21"E, 33d57'11.83"S)
Lower Right ( 25.0570905, -34.3590509) ( 25d 3'25.53"E, 34d21'32.58"S)
Center ( 24.8784669, -34.1559726) ( 24d52'42.48"E, 34d 9'21.50"S)
Band 1 Block=7796x1 Type=Byte, ColorInterp=Palette
Color Table (RGB with 256 entries)
0: 106,180,131,255
etc etc
</pre>
</blockquote>
<pre wrap=""><!---->
</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
===========================================
Zoltan Szecsei
Geograph (Pty) Ltd.
P.O. Box 7, Muizenberg 7950, South Africa.
65 Main Road, Muizenberg 7945
Western Cape, South Africa.
34° 6'16.35"S 18°28'5.62"E
Tel: +27-21-7884897 Mobile: +27-83-6004028
Fax: +27-86-6115323 <a moz-do-not-send="true"
class="moz-txt-link-abbreviated" href="http://www.geograph.co.za">www.geograph.co.za</a>
===========================================</pre>
<pre wrap="">
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</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
===========================================
Zoltan Szecsei
Geograph (Pty) Ltd.
P.O. Box 7, Muizenberg 7950, South Africa.
65 Main Road, Muizenberg 7945
Western Cape, South Africa.
34° 6'16.35"S 18°28'5.62"E
Tel: +27-21-7884897 Mobile: +27-83-6004028
Fax: +27-86-6115323 <a class="moz-txt-link-abbreviated" href="http://www.geograph.co.za">www.geograph.co.za</a>
===========================================</pre>
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