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TIF with 3 bands to data frame

6 messages · Swagath, Etienne B. Racine, MacQueen, Don +2 more

Original
Swagath
# 
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
3 days later
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
Roger Bivand
#
On Mon, 6 May 2013, MacQueen, Don wrote:

            

      
      
      
    

        
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

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      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: