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

[Agustin Lobo]

Thanks Sarah. But I think that package sp has an specific method of
image() for objects SpatialGridDataFrame, which is the class returned
by readGDAL(), and this specific method takes care of this problem. Check
image.SpatialGridDataFrame in package {sp}

Agus

2010/2/10 Sarah Goslee <sarah.goslee at gmail.com>:
> This may well be too simplistic an answer, but it might just be image().
>
> From the help for image:
>     Notice that ‘image’ interprets the ‘z’ matrix as a table of
>     ‘f(x[i], y[j])’ values, so that the x axis corresponds to row
>     number and the y axis to column number, with column 1 at the
>     bottom, i.e. a 90 degree counter-clockwise rotation of the
>     conventional printed layout of a matrix.
>
> x <- matrix(rep(1:10, each=10), nrow=10)
> x
>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
>  [1,]    1    2    3    4    5    6    7    8    9    10
>  [2,]    1    2    3    4    5    6    7    8    9    10
>  [3,]    1    2    3    4    5    6    7    8    9    10
>  [4,]    1    2    3    4    5    6    7    8    9    10
>  [5,]    1    2    3    4    5    6    7    8    9    10
>  [6,]    1    2    3    4    5    6    7    8    9    10
>  [7,]    1    2    3    4    5    6    7    8    9    10
>  [8,]    1    2    3    4    5    6    7    8    9    10
>  [9,]    1    2    3    4    5    6    7    8    9    10
> [10,]    1    2    3    4    5    6    7    8    9    10
> image(x) # not what you might expect
> image(t(x)) # this view matches the matrix representation
>
> What happens if you use plot(mygeotiff) instead of image(mygeotiff)?
>
> Sarah
>
> On Wed, Feb 10, 2010 at 11:17 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
>> 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
>>
>
>
> --
> Sarah Goslee
> http://www.functionaldiversity.org
>