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

[Swagath]

Hi Roger,

Thanks for your reply. You are correct, its more similar to my previous 
post. Thanks to help from Barry, i was able to convert the '.grd' file. 
Since there is also a tif file available, i was trying to skip the part 
of downloading the software and use R directly to convert into a data 
frame.

Thanks,
Swagath

On 5/6/13 10:06 PM, Roger Bivand wrote:
> On Mon, 6 May 2013, MacQueen, Don wrote:
>
>> I don't really know, exactly, but I'm going to guess.
>
> The message says that:
>
> In readGDAL("NArad_U_geog83.tif") : GeoTransform values not available
>
> which is confirmed by running:
>
> $ file NArad_U_geog83.tif
> NArad_U_geog83.tif: TIFF image data, little-endian
> $ gdalinfo NArad_U_geog83.tif
> Driver: GTiff/GeoTIFF
> Files: NArad_U_geog83.tif
> Size is 5868, 2432
> Coordinate System is `'
> Metadata:
>    TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
>    TIFFTAG_XRESOLUTION=671
>    TIFFTAG_YRESOLUTION=671
> Image Structure Metadata:
>    INTERLEAVE=PIXEL
> Corner Coordinates:
> Upper Left  (    0.0,    0.0)
> Lower Left  (    0.0, 2432.0)
> Upper Right ( 5868.0,    0.0)
> Lower Right ( 5868.0, 2432.0)
> Center      ( 2934.0, 1216.0)
> Band 1 Block=5868x16 Type=Byte, ColorInterp=Red
> Band 2 Block=5868x16 Type=Byte, ColorInterp=Green
> Band 3 Block=5868x16 Type=Byte, ColorInterp=Blue
>
> so the file is just a Tiff image, not a GTiff file. It has no
> information on its placing in space or dimensions. The table at:
>
> http://mrdata.usgs.gov/radiometric/
>
> actually says that it is a Tiff file, matched by Geosoft Grid files,
> discussed in a thread resolved by Barry Rowlingson:
>
> https://stat.ethz.ch/pipermail/r-sig-geo/2013-April/018157.html
>
> apparently by the same person who is puzzled now. The resolution is
> probably the same, so I'm not sure why the question is being repeated.
>
> Roger
>
>
>>
>> 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
>>
>>
>