On 04/24/2013 09:26 AM, Frank Warmerdam wrote:
On Wed, Apr 24, 2013 at 12:21 AM, Wim de Vries <[email protected]
<mailto:[email protected]>> 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.
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.
Thanks.
I did use PROJ4, but with GDAL I can simply read-in geotiffs (these give
info as you indicate below).
So, I can use getGeoTransform as long as the info (as below) is available.
Only thing to do is getting from meters to pixels (60mtr/pix in the
example below for both x,y) and vice versa,
cartesian 0,0 being at 0lon 0lat?
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,
[email protected] <mailto:[email protected]>
light and sound - activate the windows | http://pobox.com/~warmerdam
<http://pobox.com/%7Ewarmerdam>
and watch the world go round - Rush | Geospatial Software Developer
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