[R-sig-Geo] Reversed raster after readGDAL()

[Roger Bivand]

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
>
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>
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-- 
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