[R-sig-Geo] TIF with 3 bands to data frame

[MacQueen, Don]

I don't really know, exactly, but I'm going to guess.

The warning message refers to missing "GeoTransform" values. I find that
suggestive of information about the coordinate system. The website also
has a link to download a "TFW", which I believe contains coordinate system
information. This is supported by the absence of proj4string info in your
summary info. Try downloading the TFW file, putting it in the same
directory as the tif, and then try reading again with rgdal.

Instead, you might consider reading the file using the raster package;
conversion to a suitable data frame might be simpler from that point.

-Don

-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





On 5/3/13 5:41 AM, "Swagath Navin" <swagathnavin82 at gmail.com> wrote:

>Hello all,
>
>I am new to rgdal. I downloaded a tif file from
>'http://mrdata.usgs.gov/radiometric/data/NArad_U_geog83.tif' which i
>would like to convert into a regular data frame so that i can plot it
>using ggplot2.
>
>when i tried to read the file using readGDAL i get a warning message
>
>NArad_U_geog83.tif has GDAL driver GTiff
>and has 2432 rows and 5868 columns
>Warning message:
>In readGDAL("NArad_U_geog83.tif") : GeoTransform values not available
>
>What does it mean?
>
>Here s the summary of the file:
>
>Object of class SpatialGridDataFrame
>Coordinates:
>   min  max
>x   0 5868
>y   0 2432
>Is projected: NA
>proj4string : [NA]
>Grid attributes:
>   cellcentre.offset cellsize cells.dim
>x               0.5        1      5868
>y               0.5        1      2432
>Data attributes:
>      band1           band2           band3
>  Min.   :  0.0   Min.   :  0.0   Min.   :  0
>  1st Qu.:255.0   1st Qu.:255.0   1st Qu.:255
>  Median :255.0   Median :255.0   Median :255
>  Mean   :222.4   Mean   :231.1   Mean   :226
>  3rd Qu.:255.0   3rd Qu.:255.0   3rd Qu.:255
>  Max.   :255.0   Max.   :255.0   Max.   :255
>
>Can anyone please tell me which packages i should look into for
>converting it into a data frame so that i can plot it using ggplot2.
>
>Thanks,
>Swagath
>
>_______________________________________________
>R-sig-Geo mailing list
>R-sig-Geo at r-project.org
>https://stat.ethz.ch/mailman/listinfo/r-sig-geo