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

[Roger Bivand]

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
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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