On Wed, Apr 24, 2013 at 12:21 AM, Wim de Vries <wsvries at xs4all.nl> wrote:
> Thanks for taking the time to answer.
> On 04/24/2013 02:07 AM, Frank Warmerdam wrote:
> ...
>
> 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)
>
> 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.
>
Wim,
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.
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.
Size is 512, 512
Coordinate System is:
PROJCS["NAD27 / UTM zone 11N",
GEOGCS["NAD27",
DATUM["North_American_Datum_1927",
SPHEROID["Clarke 1866",6378206.4,294.9786982139006,
AUTHORITY["EPSG","7008"]],
AUTHORITY["EPSG","6267"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4267"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",-117],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AUTHORITY["EPSG","26711"]]
Origin = (440720.000000000000000,3751320.000000000000000)
Pixel Size = (60.000000000000000,-60.000000000000000)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 440720.000, 3751320.000) (117d38'28.21"W, 33d54' 8.47"N)
Lower Left ( 440720.000, 3720600.000) (117d38'20.79"W, 33d37'31.04"N)
Upper Right ( 471440.000, 3751320.000) (117d18'32.07"W, 33d54'13.08"N)
Lower Right ( 471440.000, 3720600.000) (117d18'28.50"W, 33d37'35.61"N)
Center ( 456080.000, 3735960.000) (117d28'27.39"W, 33d45'52.46"N)
Band 1 Block=512x16 Type=Byte, ColorInterp=Gray
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Software Developer
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