[GRASSLIST:3813] Raster shift between large & small area

[paallen at attglobal.net]

Hi all,

I have clean up some srtm dems for an entire
country using r.fillnulls.  All looks fine.

Now for an area approximately 1degree by 2 degrees
I have created streams drainages (r.watershed
stream segments), converted them to vector and
then exported them to a shape file.  The dem that
I used r.watershed on and a hill shading map from
the same dem I have exported with r.out.arc.

I have also exported the same dem & hill shading
over a smaller area appox 0.2deg x 0.2deg with
r.out.arc.

All of this I have imported into ArcGis 8.3 and
assigned a WGS-84 geographic projection.

The problem is the vector shape file of the stream
segments lines up exactly with the smaller rasters
(0.2deg) but the larger area dem is shifted.  

I have also exported out the entire country dem
and it to is shifted relative to the small 0.2 deg
square dem.

The shift appears to be 2-3 pixels (0.000834
degrees pixel dimension)

Whats up?  I have exported the entire thing twice
thinking that I made a mistake but this error is
reproducible.

Any suggestions?

Thanks,

Phillip J. Allen
e-mail: paallen at attglobal.net