Unfortunately I can’t provide the file (it’s about 2.1 GB and not releasable),
but below is the ‘gdalinfo’ dump for it.
The problem may be related to size of the input, because the same command
worked OK on a GeoTiff that is “only” 975 MB.
BTW For the 975 GB run that succeeded, the created overview was named *.ovr
rather than *.tif. Is this expected ? The guidance for ‘gdaladdo’ hints
that the created *.ovr is actually a TIFF, but that’s not true here (I tried
renaming it *.tif, but no TIFF reader could open it).
Driver: GTiff/GeoTIFF
Files: XXXXXX.tif
Size is 25733, 27840
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (-100.375165330488004,29.624901844319002)
Pixel Size = (0.000004869286704,-0.000004495684143)
Metadata:
TIFFTAG_DATETIME=2009:07:17 06:16:07
TIFFTAG_ARTIST=GeoEye
TIFFTAG_COPYRIGHT=(C) COPYRIGHT GeoEye, All Rights Reserved
TIFFTAG_MINSAMPLEVALUE=0
TIFFTAG_MAXSAMPLEVALUE=255
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left ( -100.3751653, 29.6249018) ( 100d22'30.60"W, 29d37'29.65"N)
Lower Left ( -100.3751653, 29.4997420) ( 100d22'30.60"W, 29d29'59.07"N)
Upper Right ( -100.2498639, 29.6249018) ( 100d14'59.51"W, 29d37'29.65"N)
Lower Right ( -100.2498639, 29.4997420) ( 100d14'59.51"W, 29d29'59.07"N)
Center ( -100.3125146, 29.5623219) ( 100d18'45.05"W, 29d33'44.36"N)
Band 1 Block=512x512 Type=Byte, ColorInterp=Red
Band 2 Block=512x512 Type=Byte, ColorInterp=Green
Band 3 Block=512x512 Type=Byte, ColorInterp=Blue
From: Chaitanya kumar CH [mailto:chaitanya...@gmail.com]
Sent: Monday, February 21, 2011 4:19 PM
To: Jay Jennings
Cc: gdal-dev@lists.osgeo.org
Subject: Re: [gdal-dev] Downsample with averaging?
Jay,
Can you provide a sample file that gives this error?
On Tue, Feb 22, 2011 at 1:56 AM, Jay Jennings
<jennings....@geoeye.com<mailto:jennings....@geoeye.com>> wrote:
Hello list,
(using GDAL 1.8.0) I am trying to create a 32:1 down-sampled overview of a
GeoTiff satellite image. My first thought was gdal_translate, with args such
as “-outsize 3.125% 3.125%”… which produces surprisingly high quality given the
absence of a resampling option. However I’m looking for a downsampling scheme
that creates a result pixel by averaging all relevant source pixels (I know,
for 32:1 downsample, that means 1024 source pixels for each result pixel !)
with the hope of an output that is not “speckled” or “grainy” insofar as
possible.
I also looked at gdaladdo, which does have the “-r average” resampling option…
the guidance at gdal.org<http://gdal.org> seems to suggest that it can produce
a 32:1 GeoTIFF external overview with a command like this:
gdaladdo -r average -ro XXXXX.tif 32
But that produces a surprising error message, namely:
ERROR 4: `XXXXX.tif.ovr' does not exist in the file system, and is not
recognised as a supported dataset name.
Am I barking up the wrong tree with gdaladdo for this purpose ? Anybody have
any suggestions for highest-quality down-sampling ? Thanks in advance.
--Jay Jennings
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--
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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