<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Apr 24, 2013 at 12:21 AM, Wim de Vries <span dir="ltr"><<a 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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<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></div></blockquote><div><br></div><div style>Wim,</div><div style><br></div><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. </div>
<div style><br></div><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. </div>
<div style><br></div><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><div><br></div><div style>Best regards,</div><div style><br></div></div></div>-- <br>---------------------------------------+--------------------------------------<br>
I set the clouds in motion - turn up | Frank Warmerdam, <a href="mailto:warmerdam@pobox.com" target="_blank">warmerdam@pobox.com</a><br>light and sound - activate the windows | <a href="http://pobox.com/~warmerdam" target="_blank">http://pobox.com/~warmerdam</a><br>
and watch the world go round - Rush | Geospatial Software Developer<br>
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