Hi Frank,
I see:
<GeoTransform>440720.0, 60.0, 0.0, 3751320.0, 0.0, -60.0</
GeoTransform>
given as an example in the Virtual Format Tutorial. And, I have been
looking at the GDAL Data Model documentation trying to figure out how
to compute these values for my input files. The docs say:
<begin docs>
Affine GeoTransform
GDAL datasets have two ways of describing the relationship between
raster positions (in pixel/line coordinates) and georeferenced
coordinates. The first, and most commonly used is the affine transform
(the other is GCPs).
The affine transform consists of six coefficients returned by
GDALDataset::GetGeoTransform() which map pixel/line coordinates into
georeferenced space using the following relationship:
Xgeo = GT(0) + Xpixel*GT(1) + Yline*GT(2)
Ygeo = GT(3) + Xpixel*GT(4) + Yline*GT(5)
In case of north up images, the GT(2) and GT(4) coefficients are zero,
and the GT(1) is pixel width, and GT(5) is pixel height. The
(GT(0),GT(3)) position is the top left corner of the top left pixel of
the raster.
Note that the pixel/line coordinates in the above are from (0.0,0.0)
at the top left corner of the top left pixel to
(width_in_pixels,height_in_pixels) at the bottom right corner of the
bottom right pixel. The pixel/line location of the center of the top
left pixel would therefore be (0.5,0.5).
</end docs>
But, I'm still unsure how to compute the required values. The docs
don't give units for GT(1) and GT(5), and for GT(0) and GT(3). My
data have a resolution of 0.1 deg lat X 0.1 deg lon, and the upper
left lat/lon is 40N,20W. Could you give me some pointers on how to
compute the transform values?
Thanks, again!
Greg
On Jan 9, 2009, at 10:45 AM, Frank Warmerdam wrote:
Greg Ederer wrote:
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 0.0, 0.0)
Lower Left ( 0.0, 801.0)
Upper Right ( 751.0, 0.0)
Lower Right ( 751.0, 801.0)
Center ( 375.5, 400.5)
Band 1 Block=751x2 Type=Float32, ColorInterp=Gray
NoData Value=-999
However, when I attempt to load this GeoTIFF into GeoServer, my
ultimate goal, I get:
class org.vfny.geoserver.global.ConfigurationException: Could not
obtain a reader for the CoverageDataSet. Please check the
CoverageDataSet configuration!
I have successfully loaded other GeoTIFFs into GeoServer that were
prepared by another member of our team from the same raw binary
data using IDL So, I suspect that there is something amiss with my
GeoTIFF.
Greg,
I notice you did not include a GeoTransform tag to indicate the
georeferenced
location. Without this you are not getting valid corner
coordninates and
this may be what is preventing GeoServer from reading the file.
Keep in mind that the origin in the geotransform should be the top
left corner
of the top left pixel treated as an area.
Best regards,
--
---------------------------------------
+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, [email protected]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for
Rent
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