From: "Laurence R Moore" <lmoore@usgs.gov>
Subject: RE: TIFF image tiles from the UK Ordnance Survey Errors out.
Date: Fri, 22 Mar 2002 09:46:00 -0700
Message-ID: <OF65574E21.77782783-ON86256B84.005812C7@er.usgs.gov>

We have quite a bit of experience with scanned maps in TIFF format at the
USGS.  I looked at the IFD of your file using od (Unix hex dump utility),
and it looks like the error messages you are getting are correct
diagnostics of an illegal dataset.  The RowsPerStrip tag really does have a
count of zero, and the DateTime tag has a count of 21.  Both are clearly
violations of the TIFF standard (page 31, DateTime N=20, page 39,
RowsPerStrip N=1)).
  
I think it unlikely that the file was accidentally corrupted; the overall
structure of the IFD is coherent and the content looks mostly legal.  My
recommendation is to contact the data producer.  Before doing that, I
suggest you confirm with your customer that the Ordinance Survey is the
real source of the data; we have a lot of trouble with complaints from
people who believe they have USGS data when in fact they have a picture of
a USGS map that was scanned by someone else.  On the other hand, we also
produce bad data now and then, and we like to know about it when someone
discovers the error.
  
----------
Larry Moore
U.S. Geological Survey
Mid-Continent Mapping Center
lmoore@usgs.gov
  
