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<div class="moz-cite-prefix">On 04/24/2013 09:26 AM, Frank Warmerdam
wrote:<br>
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cite="mid:CA+YzLBd=8kaX+0QPbNkC8rf_ipj1YFeC9oCrm2Jnyr_y+X68hA@mail.gmail.com"
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<div class="gmail_extra">On Wed, Apr 24, 2013 at 12:21 AM, Wim
de Vries <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:wsvries@xs4all.nl" target="_blank">wsvries@xs4all.nl</a>></span>
wrote:<br>
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<div>Thanks for taking the time to answer.<br>
On 04/24/2013 02:07 AM, Frank Warmerdam wrote:<br>
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...
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<div>Is the relationship between your images and
geographic (lat/long) coordinate space affine?
If so, a geotransform will do just fine. (ie.
is the pixel spacing uniform over the image in
terms of decimal degrees)</div>
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If I understand you correctly, it cannot be used for
e.g. a lambert conformal > cartesian (eg. bitmap x,y
pixels), because lons are not parallel and lats are bend
when being projected.<br>
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<div style="">Well, it can potentially be but that is a more
complicated case. You need to also provide a proper
definition of the lambert conformal coordinate system, and
then the affine transformation from pixel/line coordinates
to meter coordinates in that projected coordinate system.
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<div style="">For instance, another projected example is
seen in this file. The coordiante system is transverse
mercator with particular parameters and the geotransform
relates to the origin and pixel size given below. Given
this information GDAL knows how to relate pixels to
lat/long as you can see in the corners reported. <br>
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Thanks. <br>
I did use PROJ4, but with GDAL I can simply read-in geotiffs (these
give info as you indicate below).<br>
So, I can use getGeoTransform as long as the info (as below) is
available.<br>
Only thing to do is getting from meters to pixels (60mtr/pix in the
example below for both x,y) and vice versa, <br>
cartesian 0,0 being at 0lon 0lat?<br>
<br>
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<div style="">
<div>Size is 512, 512</div>
<div>Coordinate System is:</div>
<div>PROJCS["NAD27 / UTM zone 11N",</div>
<div> GEOGCS["NAD27",</div>
<div> DATUM["North_American_Datum_1927",</div>
<div> SPHEROID["Clarke
1866",6378206.4,294.9786982139006,</div>
<div> AUTHORITY["EPSG","7008"]],</div>
<div> AUTHORITY["EPSG","6267"]],</div>
<div> PRIMEM["Greenwich",0],</div>
<div> UNIT["degree",0.0174532925199433],</div>
<div> AUTHORITY["EPSG","4267"]],</div>
<div> PROJECTION["Transverse_Mercator"],</div>
<div> PARAMETER["latitude_of_origin",0],</div>
<div> PARAMETER["central_meridian",-117],</div>
<div> PARAMETER["scale_factor",0.9996],</div>
<div> PARAMETER["false_easting",500000],</div>
<div> PARAMETER["false_northing",0],</div>
<div> UNIT["metre",1,</div>
<div> AUTHORITY["EPSG","9001"]],</div>
<div> AUTHORITY["EPSG","26711"]]</div>
<div>Origin =
(440720.000000000000000,3751320.000000000000000)</div>
<div>Pixel Size = (60.000000000000000,-60.000000000000000)</div>
<div>Metadata:</div>
<div> AREA_OR_POINT=Area</div>
<div>Image Structure Metadata:</div>
<div>
INTERLEAVE=BAND</div>
<div>Corner Coordinates:</div>
<div>Upper Left ( 440720.000, 3751320.000)
(117d38'28.21"W, 33d54' 8.47"N)</div>
<div>Lower Left ( 440720.000, 3720600.000)
(117d38'20.79"W, 33d37'31.04"N)</div>
<div>Upper Right ( 471440.000, 3751320.000)
(117d18'32.07"W, 33d54'13.08"N)</div>
<div>Lower Right ( 471440.000, 3720600.000)
(117d18'28.50"W, 33d37'35.61"N)</div>
<div>Center ( 456080.000, 3735960.000)
(117d28'27.39"W, 33d45'52.46"N)</div>
<div>Band 1 Block=512x16 Type=Byte, ColorInterp=Gray</div>
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<div style="">Best regards,</div>
<div style=""><br>
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-- <br>
---------------------------------------+--------------------------------------<br>
I set the clouds in motion - turn up | Frank Warmerdam, <a
moz-do-not-send="true" href="mailto:warmerdam@pobox.com"
target="_blank">warmerdam@pobox.com</a><br>
light and sound - activate the windows | <a
moz-do-not-send="true" href="http://pobox.com/%7Ewarmerdam"
target="_blank">http://pobox.com/~warmerdam</a><br>
and watch the world go round - Rush | Geospatial Software
Developer<br>
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