[R-sig-Geo] rgdal challenges with binary ArcGrid

[Ashton Shortridge]

Hello,

A bit of version information: I'm running  rgdal version 0.5-24, GDAL 1.5.1 
installed on Debian. I'd like to read portions of USGS National Elevation 
Dataset (NED) files in ArcGrid format into R for various abusive purposes.

While the examples at the bottom of the readGDAL() manual page work fine for 
me, I get the following error when I try on one of my NED DEMS:
readGDAL(test.filename, offset=c(50,50), region.dim=c(100,100))
Error in .local(.Object, ...) :
        GDAL Error 3: Attempt to read past EOF in /{lengthy path 
removed}/../info/arc.dir.

I get the same error with GDALinfo(), and I get the same error with every Arc 
Grid I have tried. It does not appear that arc.dir has any relevant 
information for my purposes.

From the command line, gdalinfo gives the same error, but goes on to provide 
plenty of information - more of a warning than an error, perhaps. And 
gdal_translate also lists the error (also an error about failing to open the 
VAT table), but goes on to subset the grid and produce output anyway.

So... readGDAL() does not appear to have to read arc.dir to work - at least 
gdal_translate does not require it. Is there a way to "convince" readGDAL() 
to carry on with the input in spite of this error?

Thanks in advance for any suggestions.

Ashton

-- 
Ashton Shortridge
Associate Professor			ashton at msu.edu
Dept of Geography			http://www.msu.edu/~ashton
235 Geography Building		ph (517) 432-3561
Michigan State University		fx (517) 432-1671