Reversed raster after readGDAL()

I think I tripped on this same stone, but cannot find anything in my
records, perhaps it's on the lost computer.

The file test2.tif was made by plugin Interpolation in QGIS out of a
vector layer of points with nitrate concentration values, just
a simple inverse distance method. I think that the author f that
pluginis Marco Hugentobler (Marco, sorry if it's not you) to whom I'm
forwarding.

Relevant info from the metadata in QGIS for this raster:

Layer Spatial Reference System:
+proj=utm +zone=31 +ellps=intl +units=m +no_defs

Origin
424389,4.68549e+06

Pixel Size:
279.887,-279.887

NW corner in QGIS (interactive):424388.820,4685490.931
SW corner in QGIS (interactive):424389.122,4635951.740

Image with grid: 
http://sites.google.com/site/eospansite/dummy/test2gridqgis.jpg

The weird thing is that QGIS uses gdal to read the geotif files.

Agus

2010/2/10 Roger Bivand <Roger.Bivand at nhh.no>

On Wed, 10 Feb 2010, Agustin Lobo wrote:

Hi!

After

r3 <- readGDAL("test2.tif")

test2.tif has GDAL driver GTiff
and has 256 rows and 256 columns

image(r3,col=rainbow(128))

I get the image N-S reversed.

I've put an screenshot and the actual geotif image here:

http://sites.google.com/site/eospansite/dummy/test2_screenshot2.jpeg
http://sites.google.com/site/eospansite/dummy/test2.tif

Collected from:

http://sites.google.com/site/eospansite/dummy

Yes, it is flipped on the Y axis. What software made it? Could you please show the images with axes, as I think that the GTiff has a wrong sign on its y-step? What are the coordinates of the NW and SW corners of the image in QGIS? GDAL expects images to be read by row N to S, so a y-step with the wrong sign (+ instead of -) flips the image northward.

Roger

PS:

gdalinfo externally has lower left north of upper left:

system("gdalinfo test2.tif")

Driver: GTiff/GeoTIFF
Files: test2.tif
Size is 256, 256
Coordinate System is:
PROJCS["ED50 / UTM zone 31N",
? ?GEOGCS["ED50",
? ? ? ?DATUM["European_Datum_1950",
? ? ? ? ? ?SPHEROID["International 1924",6378388,297.0000000000014,
? ? ? ? ? ? ? ?AUTHORITY["EPSG","7022"]],
? ? ? ? ? ?AUTHORITY["EPSG","6230"]],
? ? ? ?PRIMEM["Greenwich",0],
? ? ? ?UNIT["degree",0.0174532925199433],
? ? ? ?AUTHORITY["EPSG","4230"]],
? ?PROJECTION["Transverse_Mercator"],
? ?PARAMETER["latitude_of_origin",0],
? ?PARAMETER["central_meridian",3],
? ?PARAMETER["scale_factor",0.9996],
? ?PARAMETER["false_easting",500000],
? ?PARAMETER["false_northing",0],
? ?UNIT["metre",1,
? ? ? ?AUTHORITY["EPSG","9001"]],
? ?AUTHORITY["EPSG","23031"]]
Origin = (424389.000000000000000,4635822.000000000000000)
Pixel Size = (345.007812500000000,194.019531250000000)
Metadata:
?AREA_OR_POINT=Area
Image Structure Metadata:
?INTERLEAVE=BAND
Corner Coordinates:
Upper Left ?( ?424389.000, 4635822.000) ( ?2d 5'20.10"E, 41d52'11.88"N)
Lower Left ?( ?424389.000, 4685491.000) ( ?2d 4'56.97"E, 42d19'2.06"N)
Upper Right ( ?512711.000, 4635822.000) ( ?3d 9'11.42"E, 41d52'24.52"N)
Lower Right ( ?512711.000, 4685491.000) ( ?3d 9'15.31"E, 42d19'14.90"N)
Center ? ? ?( ?468550.000, 4660656.500) ( ?2d37'10.89"E, 42d 5'47.83"N)
Band 1 Block=256x4 Type=Float64, ColorInterp=Gray

and:

GDALinfo("test2.tif")

rows ? ? ? ?256
columns ? ? 256
bands ? ? ? 1
origin.x ? ? ? ?424389
origin.y ? ? ? ?4636016
res.x ? ? ? 345.0078
res.y ? ? ? 194.0195
oblique.x ? 0
oblique.y ? 0
driver ? ? ?GTiff
projection ?+proj=utm +zone=31 +ellps=intl +units=m +no_defs
file ? ? ? ?test2.tif
apparent band summary:
? GDType ? ? ? ?Bmin ? ? ? Bmax
1 Float64 -4294967295 4294967295
Metadata:
AREA_OR_POINT=Area

Agus

? ? ? ?[[alternative HTML version deleted]]

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no